elongation of ASTM A436 type 2 austenitic iron

[Tmoose]

We have some grids (~1.5 inch x 3 inch rectangular bars about 1 foot long) cast for a hammer mill, and specify ASTM a436 type 2 material normalized.
Normal operating temp is probably 300 degrees F or so, maybe up to 500-600 briefly if things go wrong.

To appease some customers' desire for longer wear life we'd like to cast them out of Hihard 1 or something similar.
Folks are concerned that the NiHard's brittleness would cause a problem when some tramp iron sneaks into the mill, since there is equipment downstream from the grids that would get smashed. Our early literature states one function of the grids is indeed to act as a filter to protect that downstream stuff, so if the grid broke the tramp iron could make a me$$.

I have found no indications that A436 has any elongation worth mentioning, so if the A436 grids historically have offered sufficient smash protection, I wonder why the Nihard 1 wouldn't too.

Before doing comparative charpy or some other type of tests (perhaps I'll post the sledge hammer single point bend test if I survive), is there some obvious flaw in this reasoning?

thanks,

Dan T

 

[arunmrao]

NiHard is a no no for any impact applications. Please desist from using them. You may use manganese steel or any low alloy steel Q&T ,alternately use Hardox with hard facing. Hope it helps

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[cloa]

http://www.iron-foundry.com/astm-a436-a439-austenitic-cast-iron.html

This puts the elongation for D-2 as 8% so its small but not zero and it has significant toughness.

 

[arunmrao]

There appears to be a confusion in my understanding. Type D2 is Ductile iron NiResist , used for pumps and valve castings ,parts used in chemically corrosive conditions.

While in the hammer mill ,used for crushing, D-2 is rarely selected, it is always a wear resistant grade . Please correct me,if I have erred.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[metengr]

In my past life, I used to evaluate cast T-bars for our hammer mills which pulverized coal for cyclone power boilers. The austenitic grey iron worked very well because it was proven, could absorb impact blows against the wear bar because of the austenitic matrix and it would only wear over time because of coal abrasion. Knowing the NiHard line of materials, I would not recommend it nor would I try it. The tradeoff is one can predict wear rates using the current austenitic product line. I couldn't tolerate a hammer failure and mill wreck.

 

[EdStainless]

If the NiResist is wearing too fast then look at hard facing on it.
The material is very tough and actually has decent wear properties.

Any of the white irons would be like using glass, don't go there.

If you do look at austenitic manganese steels (14% Mn, 1% C) you will need to have them pre-surface hardened to get good results.
This can be done with impact or explosives. Rail switch guys are good at this.

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