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Sheet rolling and annealing


#1

Hi there.

I am attempting to roll my own sterling sheets. I am using a
continously cast billit.Could someone please advise me on some of
my doubts?

1.The surface of my billit is dark in color from the casting (
Not oxidized I think as adequate precaution with inert atmosphere
provided while casting ).Will I need to clean the surface of this
color before rolling? If yes which is the best possibility.

2.I am annealing on a belt furnace with a craked ammonia
atmosphere.Annealing to be done after what factor of reduction?

3.Any recommended formulae for calculation of belt speed ie to
have correct time through the heating zone.

4.The lenght of my cooling zone is twice the heating zone and
provided with a water jacket.Will the sheet emerge hot?

5.Which is the minimum temperature which will ensure that the
sheet does not oxidize on emerging from the furnace?

6.Do I need to pickle between rollings or at the end of rolling.

7.Will the surface emerge bright and shiny after the final
annealing or is the shine due to the last rolling operation or is
any other operation recommended to get the bright lustre of the
finally rolled sheet?

Replies to any or all will help. Any one with experiance who
could share their protocal for rolling???Will make my day.

Rajah.


#2

Friends I am repeating a previous request for help message which
seems not to have any takers. Hope some one out there will catch
on this time and interact to help out with suggestions or leads.

Thanks
Rajah.

Hi there.

I am attempting to roll my own sterling sheets. I am using a
continously cast billet.Could someone please advise me on some of
my doubts?

1.The surface of my billet is dark in color from the casting (
Not oxidized I think as adequate precaution with inert atmosphere
provided while casting ).Will I need to clean the surface of this
color before rolling? If yes which is the best possibility.

2.I am annealing on a belt furnace with a craked ammonia
atmosphere.Annealing to be done after what factor of reduction?

3.Any recommended formulae for calculation of belt speed ie to
have correct time through the heating zone.

4.The lenght of my cooling zone is twice the heating zone and
provided with a water jacket.Will the sheet emerge hot?

5.Which is the minimum temperature which will ensure that the
sheet does not oxidize on emerging from the furnace?

6.Do I need to pickle between rollings or at the end of rolling.

7.Will the surface emerge bright and shiny after the final
annealing or is the shine due to the last rolling operation or is
any other operation recommended to get the bright lustre of the
finally rolled sheet?

Replies to any or all will help. Any one with experiance who
could share their protocal for rolling???Will make my day.

Rajah.


#3

Rajah. My 40 years+ working in the industrial gas business tells
me that you are not getting an oxygen And or moisture free purge.
Very likely the nitrogen you are using has too high an impurity
level. This could originate in the gas you are using or in your
handling methods. In the US today Oxygen and moisture levels will
generaly be at or below the 1ppm by volume lwvel. Sometimes very
much less. For generAl metalurgical practice this is very
suitable. Levels of oxygen above 10ppm may cause problems higher
levels still generally always will. If you nitrogen source isn’t
good you Argon probably isn’t much better, if at all. The
addition of Hydrogen (Forming gas) at 5% hydrogen or less may
help- . Forming gas helps in belt furnaces but the hydrogen
won’t brighten up the metal except at much higher levels possibly
straight hydrogen which will brighten surfaces with enough heat
and time. Generaly forming gas just helps a less than perfect
furnace work.Hydrogen used should also be of very high purity
which is easy to get in the US. There are many potential problems
and your situation may be complex. It is difficult to solve
without analytical tools and experience. Start with your gas
source. Then check impurity levels at the use point. Jesse


#4

Rajah. My 40 years+ working in the industrial gas business tells
me that you are not getting an oxygen And or moisture free purge.
Very likely the nitrogen you are using has too high an impurity
level.

I have been using Nitrogen 99.999.I’ll check it in ppm.Today I
cast with argon.Assay specs for oxygen not known I’ll check on it
hte next time around.

1.If I use forming gas purging in the caster crucible
willitnotexplode?

2.I am purging my furnace with hydrogen/nitrogen from an ammonia
cracker.Will the annealed sheet emerge bright??

Many thanks for your suggestions.I will be attempting my first
annealing operation using h2/n2 from the craker.I have yet to set
the cycle times etc.Hope the surface emerges bright??

Rajah.


#5

Rajah. Who is your n2 source? I wouldn’t bet on 99.999 outside
the US or real time first world.Argon will not generaly be
better than this. If the forming gas is right 5 % h2 or less it
won’t burn or explo Jesse