What is Al Casting Grade A, B, C, ...? 2

[RodHot]

I am getting some aluminum(A319) investment castings made.
One is a bowl shaped part that will hold fuel.
I am switching from sand castings to investment.
I keep hearing people talk about grades of castings, A, B, and so on. How do I determine what grade of casting I need, or is there a chart with list of grades A, B, C,...?

 

[metengr]

Are you sure about this specification for aluminum castings? ASTM A319-71(2001) applies to Standard Specification for Gray Iron Castings for Elevated Temperatures for Non-Pressure Containing Parts.

 

[RodHot]

The aluminum cast material used for the sand casting is - Aluminum A356.0-T6. I am trying to understand what the casting company means when they say, "grade A, B, or C" for the casting.

 

[metengr]

Here is a reference chart for various aluminum alloys and investment cast designations. They refer to Class instead of grade.

http://www.uni-cast.com/alloy.htm

 

[swall]

A letter prefix on an Aluminum Association casting designation indicates a modification to the original, registered composition for the alloy. For 319 alloy, the A prefix indicates 3% max zinc vs 1% max for the original 319. For 356 alloy, the A indicates .2max Fe,.1max Mn and .1 max Zn as opposed to .6 max, .35 max and .35 max respectively for those elements in original 356 alloy. I am curious about the proposed switch both in alloy and process for your part. Alloy 319 is not rated as highly as 356 for pressure tightness, fluidity and hot tearing resistance. The first, pressure tightness, indicates that 319 would be more prone to leak in your application compared to 356. The latter two ratings relate to castability and indicate a problem for investment casting of this alloy. With investment casting, you don't have the ability to control the thermal gradients like you do in sand casting (i.e. in sand casting, you can place chills). So, with 319 investment cast, you will be more likely to get shrinkage and hot tears compared to sand casting and doubly so in changing from 356.

 

[lgearhart]

Being an aerospace kind of metallurgist, whenever I see "Grade" or "Class" on a casting, I immediately think of Mil-Std-2175 "Castings, Classification and Inspection of". While it was superceded by AMS 2175, you can still read it at ASSIST. In that document, Class translates into how much you have to inspect the lot of castings, and Grade refers to the acceptance levels, or how many defects you can have and how large they can be. The tables are included in the spec.

The chart that Metengr referenced notes classes, but for the ASTM specifications. I believe that in those documents the Class refers to strength. That includes not only different acceptable strength levels, but also differentiates between those casting lots for which you need separately cast test bars and those for which you have to cut a test bar out of the casting.

 

[lgearhart]

Yep, spoke too soon. Metengr's chart notes strength classes for US MILITARY specs, not ASTM specs. Those, indeed, are strength classes rather than quality classes.

 

[metengr]

Igearhart;
Don't fret about speaking too soon, I suffer from the same phenomenon. Funny though, when it comes to talking with my spouse, the opposite effect happens.

Oh well… After reviewing my ASTM Specifications in the home office, Grades A, B, C and D refer to radiographic (x-ray) quality castings purchased under ASTM A 686 "Aluminum Alloy Castings, High Strength"

I would suggest going to the web site below and purchase yourself a copy of this Standard;

http://www.astm.org/cgi-bin/SoftCart.exe/index.shtml?L+mystore+gyhm8818

 

[metengr]

Correction ASTM B686.

 

[RodHot]

Thanks guys, the Mil-Std-2175 spec was exactly what I was looking for and answered all my questions. Good Job!!

 

[sbi]

Just a reminder: ALL castings are porous

that is why we inpregnate anthing that gets close to any
petro chemecal

Mogal B Mil spec - 276A

SBI
Central Ne.,USA