4D/4C/60K Tensile fail

[RAJMETALLURGY]

Grade :4D/4C/60K
Tensile strength fail

Required value: 690 MPa min, but actual value: 664.62 MPa
Heat Treatment: Quecnch @ 930, 4 hrs soak & Tempered @ 660 Deg C 5 hrs soak.

What is the reason for tensile failure.

 

[metengr]

Send the failed sample to a competent lab for metallurgical analysis.

 

[EdStainless]

Either the Chemistry is off, or the HT is off.
Only lab work will tell you which is at fault.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[arunmrao]

Rajmetallurgy

Generally, you give more than what you get. Unfortunately in your case, you seem to be leaching the forums, by double posting and not contributing in any of the discussions taking place. Hope, you change soon enough.

I'm just one step away from being rich, all I need now is money.
( read somewhere on the internet)

 

[Guest102023]

Grade :4D/4C/60K
Tensile strength fail

Not really a question, and I have no idea what those materials are.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[RAJMETALLURGY]

Dear All,

All my chemical elements are ok and heat treatment also ok. In single heat treatment cycle I have loaded 3 samples, composition is not much different. But 2 samples were failed and only 1 is pass.

Dont know Y ????

@arunmrao: I am just seeing everyone's post, all their answers are very generic and as a metallurgist I can also tell the same. But I want to know the real root cause or any person who faced this already and I need a solution from them.

We have only optical microscope, from that I cant identify the root cause because the pass and fail micro-structures are looks similar. What kind of analysis I have to do further (SEM + EDAX). Am also searching the facility for the same.

Last time I have posted all my problems in one post, someone said dont post all the problem in one thread, So I have posted it separately.

 

[FennLane]

Your comments make little sense in any real terms.

If the Chemistry is OK and the heat treatment is OK why is it not strong enough.

What is the precise chemistry?

Have you done a hardness test as a basic check?

What can you learn from the fracture surface and nature of the tensile failure and what is the reduction in area/elongation.

You could have either grain growth issues or some intrinsic defect or more likely just a lack of control of some part of the process/testing.

 

[metengr]

Regarding chemical composition - elements are stated in material specifications in ranges from min to max or max values and do not necessarily mean that this will guarantee meeting mechanical properties. Suppliers like to have flexibility in using non-specified elements and specific combinations of stated elements to achieve properties.

 

[weldstan]

Whereas you don't provide the chemistries or the thickness of material coupons, how do you expect a rational answer?
Why have you selected the long soaking periods and temperatures? Thickness related? Chemistry related?

 

[arunmrao]

@Rajmetallurgy,
All the above comments are reasonable and justified. Next time, if you participate in a discussion, provide complete details , like grade, actual chemistry, heat treatment cycle, actual mechanical properties, microstructure, ndt reports, profile of the casting.

This will give the experts ample guidance to share their opinions. Do not self certify, that they are as per spec and that you have a problem. It does not help any one.

WCB, WCC, WC16, ASTM 148 form the bulk alloys for a good steel foundry. If you are having trouble handling them, suggest you engage the services of an expert.

I'm just one step away from being rich, all I need now is money.
( read somewhere on the internet)

 

[RAJMETALLURGY]

Failed Heat Passed Heat
C 0.21 0.19 (0.23 Max)
Mn 0.88 0.83
Si 0.44 0.51
P 0.025 0.027
S 0.012 0.012
Cu 0.02 0.02
Ni 0.36 0.24
Cr 0.13 0.1
Mo 0.01 0.01
V 0.001 0.001
N 0.015 0.01
Al 0.097 0.05
Ti 0.041 0.029
Zr 0.003 0.002
Sn 0.003 0.003
Se 0.019 0.015
Pb 0.001 0.001
Sb 0.018 0.015
As 0.007 0.008
Cequ 0.41 0.368
Res 0.521 0.371

Required value: UTS: 690 MPa min, but actual value: 664.62 MPa
Heat Treatment: Quench @ 930, 4 hrs soak & Tempered @ 660 Deg C 5 hrs soak.

Soaking given based on the thickness of the casting. All the mechanicals tested in test bar only.

I have so many heats with the above chemistry is ok in mechanicals only few heats are getting failure.

 

[weldstan]

Al content too high. Assuming the test bar is not the same thickness (much thinner) as production casting, 660 C tempering temp is too high and hold time is too long.

 

[arunmrao]

I agree with weldstan, your Al content is way too high. It indicates, that there is a process control issue.Try and look for a paper from Flowserve on Aluminium Nitride in carbon steel castings. I have a reprint of it, but cannot find readily.

I'm just one step away from being rich, all I need now is money.
( read somewhere on the internet)

 

[RAJMETALLURGY]

Tempering temperature range is given from our customer, the range is 620 - 680 Deg C. We have done some testing in lower side tempering temperature also but still its not working. Some of the heats have Aluminium less than 0.06% and that also getting fail.

Soaking hrs is based on the thickness of the casting (1 hr/ inch) For example 4inch thick casting given soaking for 4 hrs and 5 hrs in tempering.

 

[mrfailure]

Maybe you need to tell your customer you need to lower the minimum tempering temperature to achieve specified mechanical properties. Achievement of the needed finished product properties is the true goal. There should be flexibility in tweeking the recipe to achieve those properties.

 

[arunmrao]

Do you have a proper tempering furnace, wherein convection heating takes place and that the temperature is uniform at least +/- 5degree Celsius .

Have you placed a thermocouple in the casting or a block of similar thickness. It is very important, for during tempering, furnace temperature need not be casting temperature.

I'm just one step away from being rich, all I need now is money.
( read somewhere on the internet)