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.

 

[weldstan]

These are very heavy wall castings WCB castings. I would advise increasing carbon content range from 0.26% to 0.30%.

 

[metengr]

RAJMETALLURGY'
Yes, the cast version of this alloy is similar to a wrought version of Alloy 825. It would appear that for castings, a two step heat treatment is required; homogenization treatment/quench followed by a lower temperature solution anneal(stabilization) and quench.

I think you need to perform a more detailed metallurgical analysis of the fracture surface using an SEM and perform metallographic examination to better understand why this heat of material has reduced ductility. If the fracture surface as viewed under the SEM is intergranular, this could be related to segregation of elements that result in grain boundary weakening. More lab work is needed in lieu of speculation or list of possible causes.

 

[Dalinus]

Could you just measure hardness after normalizing to clarify tempering temperature?
It looks like the failed sample was tempered on higher temperature than it was needed.

Increasing carbon content would probably lower impact test values, increasing Mn content would be better. Dont know your CE limitations. If there is none, is it possible to go up to 1.28 according to note B in Table 1?

Double normalizing could also help with your impact test values (not my original idea, somebody from this forum gave me this advise months ago).

Dalin

 

[mrfailure]

Just as a sanity check: What is the measured hardness?

 

[arunmrao]

@mrfailure.
Good point, you brought some sanity into the discussion. Hope, the OP will respond .

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

 

[RAJMETALLURGY]

Sorry for the delay, Hardness value is 173 HBW. I have Carbon content 0.20% & Mn 0.87% with this value am getting my mechanicals ok. But for the same chemical & same heat treatment am getting some failure also. How to solve this, please guide me.

 

[mrfailure]

Let's recalibrate this question for a moment: You started by telling us your A216 WCB casting failed yield strength and tensile requirements. ASTM A216 WCB specifies 250 MPa min yield strength and 485 - 655 MPa tensile strength. The two heats you showed revealed that only one heat failed and it failed to meet UTS (460 MPa). Otherwise, both heats met tensile and composition requirements. So before implementing changes, I want to ask if you are having a systemic problem or did you just have a bad heat?

 

[RAJMETALLURGY]

Yea its looks like systamatic, some heats are getting pass and some heats are getting failure.

 

[mrfailure]

Then I would go with what Dalinus said and lower your tempering temperature to increase strength. You really have no control from heat to heat of chemistry since you are in spec anyway for WCB and individual melts can vary withing the composition range, so you must solve this problem in terms of heat treatment. You also have other heat treat options available to you under A216 including (if your customer approves) quench and temper under the supplementary requirements.

Good luck.