Copper Cast Bar cracks during hot rolling

In continuous casting and subsequent hot rolling of copper rod, we are facing problem of cast bar cracks during hot rolling.

Can anybody guide me in order to control these cracks which cannot be seen in the cast bar prior to hot rolling but reflect in rod as "CROWS-FEET" and rough rod surface.

Hello again Milind,

From previous threads in this Forum, we are aware that you said you are using copper scrap with no Electrolytic Tough Pitch (ETP) copper. The following question was then asked of you (November 10, 2009 www.wirenet.org/forum/viewmessages.cfm?Forum=12&Topic=754 ) by Spectre07: "Not to play with words but is your scrap 99.96% pure copper scrap or is your copper scrap 99.96 pure copper?" You never replied to this query or provided us with any other information and this left us all scratching our heads.

Moreover we have no idea as to where your copper scrap is coming from and how much oxide, sulfate,sulfide and other contaminants are on the surface this scrap. We also don't know the average size of your scrap pieces of copper and their history before being reclaimed in your process.

I personally suspect your problem is copper contamination by perhaps copper alloys or other metals but it seems to us that it is impossible for anyone to resolve this issue because of the great percentage of the scrap copper being used. Everything is on "shifting sand" so to speak.

The only way to get back on a firm footing is to experiment with 100% Electrolytic Tough Pitch (ETP) copper and thereby take all of the metallurgical variables out of your problem.

ETP C11000 is the most popular form of pure copper and is the standard electrical wire grade of copper (C11000). This grade contains 99.95% Cu, 0.03% O2, and less than 50 ppm metallic impurities. It has a high electrical conductivity, in excess of 100% IACS. In the as cast form it is called electrolytic tough pitch (ETP) copper.

Please let us know how that experiment worked out. Thank you.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641-3212

This with reference to Mr Milind's question above.
We took a random sample of the scrap we use and did a spectroanalysis.

The copper scrap has the following elements present :
Name of % of Composition
Element
Zinc (Zn) = <0.0015
Lead (Pb) = <0.00030
Tin (Sn) = <0.00020
Phosphorus (P) = 0.0178
Manganese (Mn) = <0.00010
Iron (Fe) = 0.0028
Nickel (Ni) = <0.00020
Silicon (Si) = <0.00050
Magnesium (Mg) = 0.00048
Chromium (Cr) = 0.00025
Tellurium (Te) = <0.00030
Silver (Ag) = 0.00077
Aluminum (Al) = <0.00030
Titanium (Ti) = <0.00020
Copper (Cu) = 99.6

The above reason we say that copper scrap is 99.6% copper.

Copper scrap is subjected to availability and commercial viability, but is maintained at an consistent value of 99.6 % This is done by manually sorting it twice to make sure the scrap we use doesn't contain other kinds of scrap, i.e aluminum scrap, tin polishing etc

Also did a random Spectroanalysis of the rod produced:

Zinc (Zn) = <0.0015
Lead (Pb) = 0.0082
Tin (Sn) = 0.0078
Phosphorus (P) = 0.00021
Manganese (Mn) = <0.00010
Iron (Fe) = 0.0019
Nickel (Ni) = 0.0072
Silicon (Si) = <0.00050
Magnesium (Mg) = 0.00020
Chromium (Cr) = <0.00020
Tellurium (Te) = <0.00030
Silver (Ag) = 0.0032
Aluminum (Al) = <0.00030
Titanium (Ti) = <0.00020
Copper (Cu) = 99.96

I hope the above answers your query. Please suggest us with anything we can do other then using 100% Electrolytic Tough Pitch (ETP) as it is commercially suicidal.

Are you telling me that you have no dissolved oxygen or any other dissolved gases in your rod?

Please note the following ETP C11000 is the most popular form of pure copper and is the standard electrical wire grade of copper (C11000). This grade contains 99.95% Cu, 0.03% O2, and less than 50 ppm metallic impurities. It has a high electrical conductivity, in excess of 100% IACS. In the as cast form it is called electrolytic tough pitch (ETP) copper.

I am not going to manipulate your numbers but how many ppm of metallic impurities do you have?

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641-3212