Need advice with material tuning 1

[Dalinus]

Hello,

our company was asked with delivery of castings made of steel with these parameters:
1) chemical composition: C max 0.25%, Mn max 1.00%, Si max 0.50%, Cr max 0.25%, Ni max 0.35%, Mo max 0.10%.
2) CE max 0.42 (acc. to CE = C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15)
3) yield strenght min 300 MPa, tensile strenght min 520 MPa, elongation min 17%
4) CVN-20°C min 27J
5) heat treatment normalization only
The castings and test blocks have wall thickness about 35 mm.

My question is, if it is possible to reach all of desired parameters? I think for rolled steel probably yes, but for castings...
I have fear, that some of the parameters are in contradiction to others (CE versus TS...).
My greatest concern is, that when I get desired strenghts, that I will not reach desired impact energy.

Any help would be appreciated.

Dalin

 

[arunmrao]

These are achievable and are not very demanding. You need to control your grain size by adding suitable refiners and also trace elements . Good Luck, come back with your results,if you have any real problems.

 

[jwhit]

The only thing I see that I would be apprehensive about is achieving the CVN @-20C with a Normalize only. Often a double normalize, 1700f AC to room temp. followed by 1650f AC will help with impacts. Arunmrao is correct that tuning of residual elements will make a huge difference in your results. Also, P & S should be as low as possible.

 

[TVP]

I concur with the others. Fine grain size is a must, and P & S should be below 0.010% by mass for best fracture toughness.

 

[Dalinus]

Thank you all for you input. It concurs with my original informations.

I have several test blocks with chemistry:
C 0.24%, Mn 0.55%, Si 0.24%, Cr 0.07%, Ni 0.03%, Mo 0.09%(added), V 0.14%(added), Cu 0.04%, Nb 0,050%(added), Al 0.052%(added), CE = 0.40, P 0.016%, S 0.009% (it was done in induction furnace so no way to do somthing about P and S).

My original plan was do to various combinations of normalizing(920°C) and tempering(650°C) - N, N+T, N+N and N+N+T, with variation of cooling on still air and forced air.

N (forced air) - YS 387 MPa, TS 573 MPa, EL 17%, CVN-20°C 5,7,8,12 J.
N (forced air) + T - YS 400 MPa, TS 586 MPa, EL 22.2%, CVN-20°C 4,4,10,5 J.
Unfortunately I did not let to check grain size (my mistake).

I will continue with testing after double normalizing.
As my metalurgy mentor said "good luck with that material" and I hope I will have one.

Dalin

 

[arunmrao]

Why forced air cooling? Allow still air cooling and temper at least once for consistent impact values .

 

[arunmrao]

Hint: Do exactly what you do for LCB grade .