In my opinion casting of pressure containing parts should not be done. period. API 6A generally does not allow it except under very stringent quality controls. Those controls are such you will end up cutting up a large number of castings to verify the grain size and lack of inclusions and porosity.

There are some stories circulating in the oilpatch of counterfeit BOPs and flanges that instead of being forged were sand cast and were sold as OEM parts from a chinese supplier some years back and the flanges were so porous that they were weeping. the BOP actually had Cameron's name cast into the side of it. Apparently they had taken an old BOP that was worn out and made a sand casting mold from it.

Hi,

forget about sand-casting and oil-fired heating.

Goto induction melting, steel-molds and pressure casting.

And look to my previous comments on purity of material, especially freedom from water and oxides but also organics.

RHABE

Hello V P Sampath,

Can you tell me what you are trying to cast and the size of the item please?

http://www.google.com/search?client=safari&rls=en-us&q=Al.+bronze+melting+point&ie=UTF-8&oe=UTF-8

Above is the search I used for Al. Bronze.

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http://www.google.com/search?hl=en&client=safari&rls=en-us&q=aluminum+bronze+melting+point&revid=1378909305&ei=XOQ9SonBEoKL-QbRtvC4DA&sa=X&oi=revisions_inline&resnum=0&ct=broad-revision&cd=1

Below is another search for Al. Bronze which give the 'codes' for different types of mixes of bronze.

http://www.google.com/url?q=http://en.wikivisual.com/index.php/Aluminium&ei=U3Y9St7PI4O5jAer-MUD&sa=X&oi=answers&ct=result&usg=AFQjCNG2CbfrSjJYPk-TNZm5IHj41CDvkw gives the melting point of aluminum as:

Aluminium — Melting Point: 933.47 K

Bronze melts at 1223 K

This 'Bronze' MP I think is a 'basic' Bronze/Tin mix with 20% Tin. You will need to work out the percentage of Aluminum to Bronze, and adjust the temperateture for the melting point accordingly.

The Constituents of Bronze, it strengths and why other additives are used. The strongest bronze alloys contain tin and a small amount of lead. Tin, silicon, or aluminum are often added to bronze to improve resistance to corrosion. As bronze weathers, a brown or green film forms on the surface. This film inhibits corrosion.

Bronzes have a low melting point, a characteristic that makes them useful for brazing-that is, for joining two pieces of metal. The term bronze was originally applied only to alloys of copper and tin, but because of the reputation of bronze for hardness and durability, the term has been adopted commercially for many copper-rich alloys that contain little or no tin but are similar in color to bronze, including aluminum bronze, manganese bronze, and silicon bronze. Some quality brass alloys have been incorrectly called bronze. However, when the word bronze is used by itself, the alloy should contain considerable tin.

Bronze weighs about 4.71 ounces per cubic inch. Lesser grades can contain some zinc or other metals; if zinc, the resulting properties are closer to brass.Bell bronze is an alloy of about 80% copper and 20% tin— for millennia, this has proven to be the optimum alloy, with just the right combination of hardness and resonance, to make a beautiful sounding and long lasting bell.

As mentioned, the hardest and strongest bronze contains much tin and little lead. Alloys with a high tin content also have a low melting point. This low melting point proved to be the nemesis of Russia's great Tsar-Kolokol— often thought to be the biggest bell in the world although it's actually a little smaller than Burma's Mingun Bell— which cracked during a fire in the Kremlin before it could ever be raised from its casting pit.

But such bronzes are also preferred for intricate ornamental castings such as statues. When bronze is to be used for this purpose, lead is often added to the alloy. The result is a cheaper alloy that is easier to cut. Lead is not added, of course, to bells, because it would both weaken the alloy and deaden the sound.

This gives some of the historic use of bronze. Other uses were for Cannon.

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It depends entirely on the reason and purpose you want to use 'Al. Bronze', and whether it is the right or should that be the correct metal to use. It is strong but, only when cast very thick. Hence the thickness of bronze guns and cannons, often 4" (100 mm thick), or more.

If you want to use Al. Bronze for the colour only, and the strength is not important, as, although you may be casting a 'pressure vessel', if its pressure is only a few atmospheres, it matters not. However, annealed sheet Al. Bronze is stronger and would be suitable up to a finite pressure.

It may be that Al. Bronze is your choice for a small casting to use as a demonstration say, in a science museum or similar. As long as the pressure is relatively low, there should be no danger to the public. But if you want to make a larger dome for instance, I would choose annealed Al. Bronze. Or perhaps 'wrought' Al. Bronze. Though in that case the smallest amount of Al. inclusion would work better, as it may well split under the hammering. The bronze is strong but the Aluminum is not so strong.

I look forward to your reply. Sorry this is late. I fell asleep while researching it last night!

bb

Halo Everbody,

Many thanks for the quick responses.

Let me give more details to get closer to what I seek in the information.Sorry for having not given the same earlier,inadvertantly.The Al. bronze what I refer to is typically consisting of 80%CU,10%Al,Fe4%,Mn1%,Ni5% and traces of other elements like Si,Pb etc. The item for casting is flanged Butterfly Valve bodies of 150 lbs rating ANSI class of varying nominal bore sizes from 8" to 30". Also, is any heat treatment mandatory to Al. Bronze castings of similar chemistry? Though, sand castings of Al. Bronze are predominantly used as well as permitted by manufacturing Codes of construction to manufacture valve bodies, is it potentially an unsatisfactory method to get quality casting? Or better control of melting and pouring would bring in good results? Is oil fired heating is prohibited to cast to get defect free Al. Bronz. casting? Most of the defects such as pores / inclusions are found after final machining of bore diameter. Some times defects are not visible to eyes but leak through body on pressure hydro testing. Can we get defect free / pore free Al. Bronze of radiographic quality? Suggest best practices for Al. bronze casting to improve the sand mould and oil fired technique.

Kindly enlighten.

Regards,

V.P.Sampath

Hello V P Sampath,

Just a couple of remarks.

Am I right in thinking you have the casting done by a casting company? If so there should be no problems with it.

If I were you I would get at least one item heat treated before working on it, just to see what difference it makes. You with likely be given the choice of how the item is heat treated. They may suggest more heat around the lip or area you machine?

The other possibility is that the angle between your cutting tool and the face of the work piece is not correct. Which means you could be 'gouging' instead of cutting? Doing this leaves a slightly rough and 'unfinished' texture, where you really want a smooth textured surface for a complete seal.

Can I have your opinion on this please? And, is there any chance of a pic or two?

bb

Not sure but have you tried these people, they have given us help in the past with technical queries regarding investment casting and the like.