Reduce Yield to Tensile ratio

[ShirishGaikwad]

Hello Experts!

We are producing Gx4CrNi13 (1.4317) with following composition:-

C = 0.013 %, Si = 0.41 %, Mn = 0.47 %, P = 0.027 %, S = 0.0062 %, Cr = 12.33 %, Ni = 4.71 %, Mo = 0.422 %, Al = 0.046 %, Cu = 0.181 %, Co = 0.0017 %, Ti = 0.005 %, V = 0.011 %, W = 0.032 %, Pb = 0.002 %, Sn = 0.009 %, Ca = 0.0010 %, Fe = 79.9 %

I want to know, what is the procedure of reducing the yield to tensile ratio? In our case the ratio is 0.91 but the customer has specified 0.70

Required: Yield = min.500 ,Tensile = min.760, Ratio = 0.70

Please advise what we should do to reduce the ratio.


Kind Regards
Shirish Gaikwad

 

[EdStainless]

How close is your UTS to the min required?
Typically tempering at higher temperatures will achieve this.
I presume that this material is being quenched and tempered.
Though at that C this is likely a ferritic stainless and not martensitic.
Are you sure that you didn't anneal at too high of a temperature?
Did you quench from anneal? You should, secondary phases will increase hardness and reduce toughness.
And this being a cast material you may need to take special steps to achieve a finer grain size.
Are you meeting the required elongation?
Is there an impact toughness requirement?

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P.E. Metallurgy, Plymouth Tube

 

[ShirishGaikwad]

How close is your UTS to the min required?
(UTS achived is 772 MPa against min. required of 760 Mpa.)
Typically tempering at higher temperatures will achieve this.
(Temped twice first at 620 deg. Cent. and second at 575 deg. Cent.)
I presume that this material is being quenched and tempered.
(The material is normalized at 1010 deg. cent. and later tempered twice )
Though at that C this is likely a ferritic stainless and not martensitic.
(Actually standards mentiones max. allowable carbon which is 0.06 max. we have maintained at 0.013, but the grade is still martensitic).
Are you sure that you didn't anneal at too high of a temperature?
(We have not annealed)
Did you quench from anneal? You should, secondary phases will increase hardness and reduce toughness.
And this being a cast material you may need to take special steps to achieve a finer grain size.
Are you meeting the required elongation?
(Yes we are meeting elongation requirement achived is 22 % against required 15%)
Is there an impact toughness requirement?
(Yes required is 50J but we are aiming higher at present it is 82J)

 

[EdStainless]

Are you sure that you are not reporting a YS that is too high?
Maybe because of where your software has taken points for the offset you have come up with a YS that is too high.
At that C this material is only faintly martensitic.
I am a bit concerned that you have spent too much time at too high of temperature.
I don't see a reason to go above 925C, and when we weld this alloy we anneal at 850C.
You should look at the grain size, you may have blown it up.
There is little in the structure to pin the grains and they will get very large.
With the rest of your properties I like your results.

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P.E. Metallurgy, Plymouth Tube

 

[MagBen]

with a tensile of 772mpa, ratio of .91, your YS be 702 that is large for this alloy. The way to decrease UTS/YS are often implemented by decreasing YS (without much decreasing UTS) and/or decreasing work hardening rate. So if you have course grains, this maybe a good thing because it decreases hardening rate.
one thing to try is to increase your temper temperature, the ratio could be decreased due to more reversed austenitic phase transformation. Your toughness may also be increased.
Another thing to watch is the cool rate at normalization. how big is your part? why did not you quench?