WCB Tensile Failure

[RAJMETALLURGY]

WCB with Normalized (940 Deg C) & Tempered (640 Deg C) are getting failure with lower yield and lower UTS. Please guide me to resolve it.
Similarly in the case of Inconel 825 (CU5MCuC) getting failure in elongation (Solution annealed 1900 Deg C & Stabilized @ 960 Deg C). How to solve it, the fracture surface looks like brittle fracture no appearance of cup & Cone.

And is it required to add Ti & Al in the case of Carbon Steel (WCB, LCB) & Low alloy steels (WC6, WC9 & C5). Because am not getting toughness value @-10 deg C. If I stopper am getting good values in +20, +10, 0 Deg but in -10 Deg am not getting more than 27 Joules.

Please help me.

 

[Guest102023]

WCB?

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

 

[arunmrao]

ASTM A 216 WCB grade is a simple grade to cast. If your UTS and YS values are low, recheck your chemistry and trace elements . Also, check your temperature during normalizing.

What is your residual Al in LCB, WC6 etc. There is no requirement to add Ti for thee grades. What is the heat treatment cycle for LCB grade?

In order to get specific advice and responses, do not cloud too many issues in one post. Discuss each issue separately, it will help, else you may be considered in poor light.

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

 

[RAJMETALLURGY]

arunmrao: Thanks for your response. WCB chemistry is within the specification of ASTM A216. And I have normalized the material @940 Deg C only.

My residual Al is 0.06 - 0.08%, For LCB we are doing quench & tempering but sometimes we are adding Nickel to achieve impact value but impact is getting fail. What I have to do?

And please suggest me in the case of Inconel 825 (CU5MCuC), elongation failure after solution annealing & stabilizing.

Next time I will post the issues separately.

 

[metengr]

I agree with arunmrao, your carbon content is probably too low. SA 216 provides a maximum carbon content of 0.25% by mass, there is no minimum. Re-adjust your chemical composition for this grade.

Inconel 825 -

http://www.sandmeyersteel.com/A825.html

"Alloy 825 has good mechanical properties from cryogenic to moderately high temperatures. Exposure to temperatures above 1000°F (540°C) can result in changes to the microstructure that will significantly lower ductility and impact strength. For that reason, Alloy 825 should not be utilized at temperatures where creep-rupture properties are design factors."

There is no reason to perform a stabilization heat treatment for this alloy.

 

[weldstan]

Also check the Mn content.
While not germane to grade WCB, I have recently looked at MTRs for SA-106B where Mn was < 0.44%. While the ambient temp properties meet the requirements, don't expect the same for the higher temp. properties. And as for impact toughness properties - forget about it!!!

 

[arunmrao]

@rajmetallurgy,
Perform a search in this forum for "LCB grade castings", you will see several good discussions.

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

 

[jwhit]

For WCB I'd shoot for .18-.22 C, Mn around 0.6-0.9, Al<0.07(for weldability) Ti<0.05. Try a double normalize for impact strength, first at ~1700f, second at ~1650F followed by a temper at ~1200F. You should be able to hit the mechanicals, have excellent weldability with a low CE. Also, use the cleanest metal possible, low P & S as well as free of refractory materials from prior use of your revert. If you want exceptional properties go the AOD route. Use the same composition for LCB but do a water quench and temper.
I can't help out with the 825 alloy.

 

[arunmrao]

jwhit,

AODs in steel foundries has not been popular. The smallest AOD to my mind ( subject to correction) is about 5 tons capacity. Most steel foundries operate in batch of 1 ton .

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

 

[jwhit]

Arun,
I know that, however I also know of foundries who send their revert out for AOD processing and a local foundry has a small vessel so it isn't unprecedented. It all depends on how critical the work is.

 

[arunmrao]

Thanks.

WCB,LCB, WC 6/9 grades are very common and straight forward for any valve casting manufacturer. If a foundry fails to achieve the metallurgy for these alloys , my advice would be, either upgrade or move away.



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

 

[jwhit]

I certainly agree that if they can't make those alloys, they can't make anything else either, or they haven't looked hard enough at residual/tramp elements that have gotten in to their scrap stream. Had a situation a few years ago where impacts in 165-150L low alloy had issues with impact test results. Found that one of the scrap sources had high Nb content. Got rid of it and the problem went away.

 

[RAJMETALLURGY]

thanks ,

@metengr,

But as per ASTM A494, for CU5MCuC "Heat to 2100°F [1150°C] minimum, hold for sufficient time to heat castings to temperature, quench in water. Stabilize at 1725-1815°F [940-990°C], hold for sufficient time to heat castings to temperature, quench in water or rapid cool by other means".

So how can I skip the stabilization process.

@arunmrao & @jwhit,

I have attached the chem & mechnical of 2 heats. For me few heats only getting failed and most of the heats are getting clear with out any AOD, VOD process. Please see the spec and what tramp elements I can control to achieve the mechanical in WCB.

Please suggest me.

 

[RAJMETALLURGY]

WCB (Normalized 940oC, 6 hrs soak & Tempered 650 oC, 7 hrs soak) Analysis:

Element Pass Heat Chemical Fail Heat Chemical
C 0.21% 0.20%
Mn 0.87% 0.93%
Si 0.46% 0.35%
P 0.017% 0.019%
S 0.013% 0.011%
Cu 0.09% 0.010%
Ni 0.03% 0.020%
Cr 0.10% 0.15%
Mo 0.012% 0.008%
V 0.005% 0.011%
Nb 0.004% 0.005%
N 0.014% 0.013%
W 0.007% 0.007%
Al 0.039% 0.044%
Ti 0.001% 0.002%
Zr 0.004% 0.005%
Sn 0.004% 0.004%
Fe 98.01% 98.09%
CEq 0.386% 0.391%
Res 0.237% 0.199%
Se 0.002% 0.002%
Pb 0.001% 0.001%
B 0.001% 0.001%
Sb 0.001% 0.001%
Zn 0.001% 0.002%
As 0.006% 0.005%
Bi 0.002% 0.008%
Ta 0.018% 0.027%
Ca 0.001% 0.001%
Ce 0.040% 0.039%
La 0.022% 0.027%
Co 0.003% 0.003%
Y.Sgth 295.79 MPa 269.29 MPa
UTS 504.42 MPa 459.82 MPa
%E 36.28% 40.32%
%R 57.28% 66.82%

 

[arunmrao]

The carbon content will have to be raised to 0.24-0.26% .Why are you having 6 hrs hold time at 940C ?

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

 

[Dalinus]

What are the dimensions of test blocks?
What type - attached to castings, separately cast.
Were they heat treated on the same place in furnace? With castings or separated?
What is the grain size?
Any visible defect(microporosity, hole,...) on fracture of the tensile test specimen?
The chemistry is from the test block or heat sample?

 

[RAJMETALLURGY]

@arunmrao

Some of my customer asking 0.25% Max. Depends upon the casting thickness we are giving soaking time.

@Dalinus

Its normal keel block - 230mm length and 25 mm thickness.
separately cast
with casting
Grain size will be 7
Hmm, no visible defects.
chemistry from heat sample. (sometimes chemical is getting varied between test block and heat sample.

 

[arunmrao]

WCB has carbon content of 0.3%max, there is no minimum specified.

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

 

[jwhit]

I didn't see anything in the chemistry that jumped out at me. One of the newer requirements above and beyond A216 for WCB is restricted carbon, often 0.23% max with a CE of 0.41 or 0.43% max. This is driven by the NACE MR0103/SP0472 and MR0175 requirements, among others. These carry over to all ASME IX P1 carbon steels. We meet the mechanical property requirements for WCB consistently while meeting these composition limitations. Things are getting tougher for the foundries.
Are you decarburizing the test material extensively with a 6 hr. hold? Are you getting a cup and cone tensile fracture? Any possible issues with location of the test material in the furnace? If anything else comes to mind, I will add it.

 

[jwhit]

How many times are you recycling your revert and how much of the charge is made up of revert? Melting practice also can enter into this issue, with Arc melting doing a better job of refining than induction. Sometimes, of revert is remelted too many times a condition often referred to as dead metal will occur. It is characterized by a crappy(good technical word)appearance, and poor mechanicals. Your elongation and reduction values don't indicate that this should be a problem, but it is always good to be aware of. I've never found a good answer as to the exact cause of dead metal, but believe it to be build up of residual gases (hydrogen) plus dirt in the metal.