Casting defects

[priyam07]

Hello guys,
I have an interesting looking crack like feature with inclusions in a low alloy steel casting. Heat treatment: Normalized-->quenched and tempered in water.
Any thoughts on how, why and it's effects on the properties of the part?
Cheers!

 

[weldstan]

Looks like a non-fused chaplet.

 

[arunmrao]

Let us know more about the casting. The location of the defect and at what stage of processing was this noticed.

Have you performed a D.P or MPI to confirm it is a crack.

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

 

[priyam07]

As you can see this is at 200X optical, mostly seen at the dendritic segregation zone. I will try to find a low magnification image to show the microstructure.
This can be found all over the casting and this particular image is from a polished sample cut for CVN testing of the finished product.
Thanks!

 

[priyam07]

Here you go at 50X.

 

[CoryPad]

The first picture looks like oxide film type defect such as that from flux/mold powder.

 

[arunmrao]

The second picture looks like a crack and seems that there is segregation pattern ,but finding it all over the casting surfaces is baffling.

Was there a change in scrap ?

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

 

[priyam07]

Yes, mostly in the segregation in different shapes. Looks like oxide films and sometimes connecting the MnS inclusions might result in crack like features!
So, any idea why they form or anyone has seen something similar in steel castings? and does this really have any effect on the impact toughness of the cast part?
Appreciate your input, thanks!

 

[weldstan]

Looks like segregation and cracking originating therefrom.
In the past few years, I evaluated two failures in wrought carbon steel products, originating at highly unusual, shaped segregation near the surface. I did not take the failure to primary manufacturing (continuous casting?) method. Rich in Ca, Si, Mn.

 

[priyam07]

Thanks guys, appreciate it. For sure this adversely affects the toughness of the casting when compared to just MnS (type II) inclusions in the segregations area.

 

[EdStainless]

perhaps related to revert not being clean and/or fully melted in?


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