Casting Brass For Machining Stock

Hey all!
First, I'm sorry it has been such a long time since I have posted. I have been busy with other hobbies/projects but not much casting.
I am interested in casting some 85,5,5,5 brass to use as machining stock. I have had success casting this for machine stock on the past. (See below) I don't like the color of C360 much and that seems to be the most readily available alloy. I also have a bunch of red brass that I bought from Anon. It's color is great but it was cast with a lot of porosity and does not look good machined due to this. I am considering re-casting it to see if I can improve it. I have some Phosphorus Cu rod I can add for degasing. How much rod should I add and what else can I consider to improve this alloy?



As far as I can tell, I cannot buy Red Brass 85,5,5,5 or something close in bar stock. It sounds like I may have to go with a bronze? What alloy of bronze has a nice red color when freshly machined? Silicon bronze looks good but doesn't machine very well.

Robert

 

It's commonly available as continuous cast bar, the foundry I help out at, uses it by the ton. We call it LG2 leaded gunmetal but it's also SAE40 or C836 bronze. We do skim, flux and then skim again if recycling old castings and the castings seem to come out fine. Scraping the inside of the crucible lightly while it's full of bronze with a preheated skimmer will cause any contamination to come to the surface to be skimmed. Good hygiene: not using badly corroded scrap, plenty of skimming, even it it loses some bronze with the dross and a light flux and skim just before pour. A small chunk of hardwood on top will burn and reduce oxidation too although it can get in the way.

It's great stuff, I love it: salt water resistant, good bearing qualities, machines well and usually makes good tight non porous castings.

 

Thanks Mark. I see it is commonly known as 836. Unfortunately, not much available on ebay or from my usual suppliers.
Robert

 

if it cast with Porosity you probably picked up gas, Degas using 1.5 Ounces of Phospor-copper/ 100 Lbs of Melt ... Plunged to the Bottom Just before pouring... dont use too Much or you will get brittle metal


V/r HT1

 

I bought some phosphorus copper welding rod from ebay. I have to research the exact composition.
Robert

Edit: Just checked. My material is 87% Cu, 6% Phosphorus, 6% Silver. Not ideal. If I used this I would be adding a small amount of Ag to the melt as a contaminant. It would be a very small percentage by weight and I doubt it would affect the properties much. There would be about 2 grams of Ag in the 10 lb melt. Any thoughts?
Robert

 

Found some at BCS
https://www.budgetcastingsupply.com/15-Phosphor-Copper-Shot-1-Lb-Bag-p/3008-001.htm

 

That is what I use

 

I weighed my material and decided I needed about 3g of Phosphor Cu for my 11 lb melt:



Added Phospho Copper after skimming:



Stirred and poured:



Shakeout:



This seems to have removed most of the porosity and it machines pretty well! Very satisfactory!



Thanks for the advice!
Robert

 

Thanks Kelly! Another hold down for starters. Probably some stainless steel Kant Twist Clamps for Christmas presents. Who know what else. Wish I could find more copper pipe!
Robert

 

If you have a razor sharp diamond honed carbide tool, LG2 can reveal some of it's grain structure when being machined: it kind of looks like the flake pattern that galvanized iron has, only smaller.



It's more visible in this photo of a repaired prop shaft bushing with white bearing metal:

 

R

 

Nice! One of my initial reasons for wanting to cast was to be able to make turning stock. A 3" piece of 2" diameter aluminum or brass is prohibitively expensive. Your level of porosity certainly looks reasonable.

 

That's the BEFORE. That is a 2" round casting cut and turned. I only had some surface defects on my cylinders.
Robert

 

OWE it hurts! it hurts!!! don"t stir, Plunge Phos CU to the Bottom and hold it there til the reaction stops... make sure everything is preheated before it actually goes in the melt.


V/r HT1