Brass cracks when rolling

Discussion in 'Castings, finishing/ repair/ and patina's' started by metallab, Nov 3, 2021.

  1. metallab

    metallab Silver

    Recently I melted some (red) copper scrap which I poured into sheet blanks of 3mm thick and about 2"x3" size. I melted the copper under a few pieces of charcoal to prevent oxygen dissolution into the Cu metal. That worked, after wirebrushing the sand off the blanks I rolled them into sheet of less than a mm thickness with a few intermediate anneals.

    I used to cast sheet blanks in a steel mold which all times resulted in incomplete castings due to premature freezing. The sand castings appear to be much more succesful.

    Now I did the same with brass, by remelting scrap, including lathings. I also got the sheet blanks but after rolling down to 1.5-2mm thickness with one time intermediate annealing it cracked. I remelted the brass and casted the blanks again, but after rolling the cracks aooeared again. Weird, because brass contains zinc which prevents oxidation of the copper.

    What can be the problem here ?

  2. HT1

    HT1 Silver

    wrong alloy, cast material should not be forged

    Here is the alloy you need

  3. metallab

    metallab Silver

    78% Cu and 22% Sn ?
    Well, amazing video. Is the man 96 years old or the company (I assume the latter) ?
  4. Petee716

    Petee716 Gold Banner Member

    Quite an interesting video. He said he was 96 in Korean years. They evidently count their time in the womb in their age, but he sure doesn't look that old.
  5. Peedee

    Peedee Silver

    I guess the first thought would be don't get metal in your eye! (Been there but got away with it more than once).

    They only work the alloy hot, but I agree with the direction of HT1,
  6. metallab

    metallab Silver

    Normally brass can be rolled cold (which is done in commercial facilities) but the structure of my brass was probably crappy. I did it again with self-alloyed 90/10 bronze and that worked much better.
  7. HT1

    HT1 Silver

    Specific brass alloys are cold rolled, forgability chart&f=false

    this is the same as people trying to cast aluminum extrusions, only WAY more complicated,
    a very small addition of some trace element can cause the formability of brass to drop significantly , melting brass is all but guaranteed to add or remove something , trying to mix casting and forming, is likely to add problems
    if you are not just trying to cast pretty plaques, you need to use known alloys, and clean tools

    V/r HT1
  8. metallab

    metallab Silver

    HT1: That is what I already thought. My brass is from remelting scrap from brass chandeliers, plumbing stuff, lathe turnings, etc, so that is not so clean.

    I tried rolling hot (putting a red hot bronze sheet between the rolls, but it immediately cools off to almost room temperature.
    How does the steel industry handle that ? They roll sheet above 1000 C which is only 10-20mm thick and they have to cool the rolls with water. Even after the last roll (10mm thick) it is coiled up to yellow hot toilet roll shaped coils of 1.5m wide and 2m diameter.
    This video shows it clearly at the beginning, a yellow hot toilet roll being coiled.

    Last edited: Nov 5, 2021
  9. HT1

    HT1 Silver

    steel is a different animal reeally there is alot going on, one the steel they are working with is huge, lots of mass to hold the heat, you are working with smaller pieces, so they cool faster,

    for the amatuer brass is much harder to work with because, by the time you see color (dull red) brass is about to melt, also it conducts heat faster,

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