Please help me to solve the following problem. We produce copper rods by horisontal continuous casting. Diameter of rod - 18 mm. Average oxigen content is about 5 ppm. We often have poor quality due to the cracks on the rod surface.
What the optimal linear speed of the rod must be(when cast occurring).
We use dispersed graphite as the copper melt cover. Is there necessary to use protective atmosphere too?
How to reduce hydrogen influence? Is it the cause of bad quality?
Is there discoloration on the surface? that would indicate oxidation, which can cause cracking. a gas blanket can solve that problem. Depending on the temperature of the copper as it exits the process you can use argon, helium, or CO2 ( in descending cost) if you really wanted to go cheap steam or a hot water bath also works, or at least it works for copper wire. The thing to consider with the hot water bath though is that it may effect the hardness of the rod. Helium and argon are the best bets if you cannot deal with the change in hardness. More details on your process would be helpful.
You cannot concast copper successfully by horizontal or vertically downwards casting modes - without cracks. It is not possible to solve this question. This is common with many isothermal freezing entities cf. pure metals, where the metallostatic head pressureon the newly solidified shell, gives rise to an excesive friction effect, which casues drag on the shell and results in cracks. Since there is no freezing range with isothermal freezing entities. then there is no MUSHY feed-thru' possible hence "healing" of the cracks IE as in copper alloys such as bronzes, brasses. etc.
Vertical upwards casting is the way to go where negative strip of the solidified shell conditions prevail and the result is NO CRACKS.
Speeds of production with upwards casting 18mm diameter rods ought to be ~
1.1 - 1.6 metres per minute using high effciency coolers. Maintenance of good thick (typ 100mm) Graphite/carbon granule covers for premelt and also for melt in holding furnace is critical - melt must not be exposed to air, where on a humid day, the moisture content can be 10,000ppm moisture - not conducive to low hydrogen contents, let alone worry about the oxygen situation.
Good luck but you will have to change mode of casting to escape cracks.
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Best thoughts Sandy Cochrane Conticast Limited UK
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----- Original Message ----- From: "Alexey Shubin" Newsgroups: sci.engr.metallurgy Sent: Tuesday, September 02, 2003 11:11 AM Subject: copper continuous casting - problem
may be true that upcasting will yield better results than down cast , but I have seen plenty of cracks on upcast OF Copper rod most likely related to hydrogen,,
The fact is that we can sometimes produce the copper rod with good quality. But the casting speed is very law(about 10-15 cm/min). Besides, when using this law speed of casting, the quality may be good, and it may be bad. We use raw material(cathodes) from one manufacturer. Graphite cover - from one source(and it is very good graphite). When casting, copper rod of diameter 18 mm goes horisontally. Regime - start/stop, about 30 cycles/min. Crystallization occurs in graphite crystallizator with water cooling(through copper wall). Than the rod release from crystallyzator, it passes some way and than goes through the second cooling - water stream. The surface of rod has normal copper color.
We know that some copper rod producers(in Russia too) use the similar method with very good results. But they solved the problem(s). Casting speed they use is about 90 cm/min and rod diameter 20 mm.
Consequently, horyzontal continuous casting of pure copper is possible. But there are some sophysticate problems( with gases in copper, or with details of cooling unit, or other).
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