{"id":31087,"date":"2026-09-07T10:19:52","date_gmt":"2026-09-07T10:19:52","guid":{"rendered":"https:\/\/doingcable.com\/?p=31087"},"modified":"2026-09-07T10:19:55","modified_gmt":"2026-09-07T10:19:55","slug":"how-to-produce-qualified-8-mm-copper-rod-from-copper-scrap-and-copper-cathode%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/doingcable.com\/tr\/how-to-produce-qualified-8-mm-copper-rod-from-copper-scrap-and-copper-cathode\uff1f\/","title":{"rendered":"How to Produce Qualified 8 mm Copper Rod from Copper Scrap and Copper Cathode\uff1f"},"content":{"rendered":"

A qualified 8 mm copper rod is electrical drawing stock that meets ASTM B49, EN 1977 (prEN 1977:2025 draft) and GB\/T 3952-2016 for chemistry, oxygen, conductivity and drawability. Two industrial routes produce it: upward continuous casting (Upcast) of oxygen-free rod from clean cathode or refined high-grade scrap, and continuous casting and rolling (CCR)<\/a> <\/strong>of low-oxygen ETP\/FRHC rod from cathode and\/or fire-refined scrap. Capacity, scrap grade, oxygen target and downstream drawing size decide which line is correct \u2014 not marketing language.<\/p>\n\n\n\n

For cable plants, 8 mm rod is the standard inlet to rod-breakdown drawing. If resistivity, oxygen or surface scale drift outside specification, the failure appears later as die wear, wire breaks, hydrogen embrittlement or failed IEC 60228 conductor tests. This article states the process windows, feedstock rules, comparison data and inspection logic used by mill engineers.<\/p>\n\n\n\n

\n
Hemen Sorgula<\/a><\/div>\n<\/div>\n\n\n\n

What is a qualified 8 mm copper rod for electrical drawing?<\/h2>\n\n\n\n

A qualified 8 mm copper rod is circular drawing stock, typically 7.92\u20138.08 mm for Upcast OF and about 7.56\u20138.32 mm for CCR ETP, with conductivity \u2265100% IACS (resistivity \u22640.017241 \u03a9\u00b7mm\u00b2\/m at 20 \u00b0C) and oxygen controlled to the selected grade. It must draw without systematic breaks into intermediate and fine wire.<\/p>\n\n\n\n

Typical commercial grades:<\/p>\n\n\n\n

Seviye<\/th>Process<\/th>Oxygen<\/th>Conductivity @ 20 \u00b0C<\/th>Typical feedstock<\/th><\/tr><\/thead>
Cu-OF \/ TU1 \/ C10200<\/td>Upcast<\/td>\u226410 ppm (often \u22645 ppm)<\/td>\u2265100\u2013101.4% IACS<\/td>Cu-CATH-1 cathode; selected millberry scrap after refining<\/td><\/tr>
Cu-ETP \/ T1\u2013T2 \/ C11000<\/td>CCR (shaft + holding)<\/td>100\u2013650 ppm; plants often hold 200\u2013400 ppm<\/td>\u2265100% IACS<\/td>LME Grade A \/ Cu-CATH-1 cathode<\/td><\/tr>
Cu-FRHC \/ recycled ETP<\/td>CCR + reverberatory fire refining<\/td>Similar to ETP if refining is complete<\/td>\u2265100% IACS when chemistry is controlled<\/td>No.1 \/ No.2 red scrap + optional cathode blend<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

ASTM B49 lists ETP oxygen at 100\u2013650 ppm and oxygen-free copper at max. 10 ppm without metallic deoxidizers. EN 1977 \/ CW004A (Cu-ETP) and CW005A (Cu-FRHC) both require max. 0.01724 \u03bc\u03a9\u00b7m; CW003A (Cu-ETP1) and CW007A (Cu-OF1) target 0.01707 \u03bc\u03a9\u00b7m (101% IACS). GB\/T 3952-2016 T1 oxygen is \u22640.040% (400 ppm); TU1 is \u22640.0010% (10 ppm). Total listed impurities for premium T1\/TU1 stock are typically \u226465 ppm excluding oxygen.<\/p>\n\n\n\n

The original claim of \u201cresistivity 0.10724\u201d is not an electrical-rod value. The IACS reference remains 1\/58 = 0.017241 \u03a9\u00b7mm\u00b2\/m.<\/p>\n\n\n\n

Which production route should a plant choose: Upcast or CCR?<\/h2>\n\n\n\n

Choose Upcast when annual volume is about 3,000\u20138,000 t, oxygen must stay \u226410 ppm, and the product is fine-wire, magnet wire or hydrogen-sensitive conductor. Choose CCR when volume is 8\u201325 t\/h (roughly 50,000\u2013180,000 t\/year on a continuous mill) and the market is building wire, power cable and general ETP drawing stock.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Upcast route (OF rod).<\/strong> Cathode or fully refined melt is held under charcoal or graphite flake so air does not contact the bath. Holding temperature is typically 1150 \u00b0C \u00b110 \u00b0C. Graphite crystallizers freeze the metal upward into 8\u201320 mm rod. For 8 mm finished rod, plants either cast 8 mm directly from high-purity cathode, or cast 17\u201320 mm from mixed\/refined melt and cold-roll to 8 mm to close porosity and improve workability. Soft-state resistivity is specified \u22640.01724 \u03a9\u00b7mm\u00b2\/m; elongation is commonly >37%; density ~8.9 g\/cm\u00b3. Drawing speed on a multi-strand Upcast line is typically 0\u20133000 mm\/min with dual-servo traction. A 1050 kg\/h melting rate corresponds to about 8,000 t\/year at ~7,920 operating hours.<\/p>\n\n\n\n

CCR route (low-oxygen ETP\/FRHC rod)<\/a>.<\/strong> Cathode is melted in a shaft furnace; scrap is melted and fire-refined in a reverberatory or tilting furnace. Metal flows through a launder into a 5-wheel caster (casting wheel commonly \u00d81800\u20132200 mm; cast-bar section ~2300\u20132500 mm\u00b2). After shear, straighten, edge shave and brush, a 12-stand two-high mill reduces the bar to \u00d88 mm at about 9.5\u201311.6 m\/s. Line output on mid-size plants is 12\u201316 t\/h; coil mass is 3\u20135 t; plant footprint excluding furnace is about 40 \u00d7 8 \u00d7 6 m. Alcoholic-water or emulsion cooling plus optional wax coat protects the surface for export.<\/p>\n\n\n\n

Parametre<\/th>Upcast OF line<\/th>CCR ETP\/FRHC line<\/th><\/tr><\/thead>
Finished diameter<\/td>\u00d88\u201320 mm (8 mm direct or 17\u201320 \u2192 8 mm cold roll)<\/td>\u00d88 mm hot-rolled<\/td><\/tr>
Typical capacity<\/td>0.8\u20133 t\/h per line; 3,000\u20138,000 t\/y common<\/td>5\u201325 t\/h; 12\u201316 t\/h typical mid-line<\/td><\/tr>
Melt cover<\/td>Charcoal \/ graphite flake<\/td>Shaft atmosphere + holding furnace<\/td><\/tr>
Oxygen in rod<\/td>\u226410 ppm<\/td>200\u2013400 ppm plant target; spec 100\u2013650 ppm<\/td><\/tr>
Holding temperature<\/td>1150 \u00b0C \u00b110 \u00b0C<\/td>Cast bar ~1080\u20131120 \u00b0C into mill<\/td><\/tr>
Final mill \/ draw<\/td>Servo up-traction 0\u20133000 mm\/min<\/td>12-pass mill, max ~10\u201311.6 m\/s<\/td><\/tr>
Installed power (process, excl. large furnace)<\/td>~410\u2013620 kVA class for 8 kt\/y<\/td>~550\u20131200 kW \/ 1000\u20131200 kVA class<\/td><\/tr>
Best use<\/td>Fine wire, OFHC, vacuum\/brazing duty<\/td>Building wire, MV\/LV power cable, high volume<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

KSH International\u2019s 5,000 t\/y Upcast plant started in Pune in 2026 specifically to close the loop on process scrap \u2014 evidence that small OF lines remain the rational choice below CCR economic scale.<\/p>\n\n\n\n

How must copper cathode and copper scrap be specified before melting?<\/h2>\n\n\n\n

Cathode for electrical rod must be Cu-CATH-1 \/ LME Grade A, typically 99.975\u201399.99% Cu with metallic impurities well below 65 ppm. Scrap for direct melt or fire refining must be sorted by copper content, coating and foreign metal \u2014 plated, tinned or PVC-coated material is not charged into an OF Upcast furnace.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Cathode rules.<\/strong> Cu-CATH-1 group limits used by refiners: (As+Cd+Cr+Mn+P+Sb) \u226415 ppm; (Bi+Se+Te) \u22643 ppm; (Co+Fe+Ni+Si+Sn+Zn) \u226420 ppm. Se, Te and Bi are the most damaging because they are almost insoluble in solid copper and form grain-boundary films that cause hot shortness and drawing breaks. Shaft-furnace CCR plants specify electrolytic Grade A and usually limit first-grade scrap blend to 10\u201315% if rod quality is tight.<\/p>\n\n\n\n

Scrap rules used on qualified 8 mm lines.<\/strong><\/p>\n\n\n\n

    \n
  • Electrolytic copper \u226599.95% Cu: charge directly to the Upcast or shaft furnace.<\/li>\n\n\n\n
  • First-grade recycled copper \/ millberry \/ bare bright: \u226598% Cu; a small fraction at 96% may be blended only after assay. No tin, nickel or other plating. Surface must be clean; PVC and other coverings removed. Only very clean bright wire may enter an Upcast furnace without a refining furnace.<\/li>\n\n\n\n
  • Typical CCR scrap mix quoted by mill builders: 60% first-grade red scrap + 40% second-grade, then adjusted after OES.<\/li>\n\n\n\n
  • Practical blend used on mixed Upcast plants: 50% electrolytic copper + 50% refined scrap melt, then trimmed to chemistry.<\/li>\n<\/ul>\n\n\n\n

    ISRI No.1 (Barley) and No.4 nodules (Clove, min. 99% Cu, no tin\/lead\/zinc\/Al\/Fe) are the scrap families that behave closest to cathode. No.2 and insulated wire require fire refining. Plating metals (Sn, Ni, Pb) and phosphorus are the usual reasons a \u201ccheap\u201d scrap lot destroys conductivity and annealability.<\/p>\n\n\n\n

    2025\u20132026 fire-refining research shows impurity removal order Sb < Ni < Pb < Sn < Fe (Zn): antimony and nickel are the hardest to slag. A CaO\u2013SiO\u2082\u2013FeO\u2093\u2013Al\u2082O\u2083 flux at ~1200 \u00b0C and higher oxygen potential can push fire-refined copper toward 99.5\u201399.9% Cu, but electrical rod still needs tight control of residual Sb, Ni and S \u2014 not only a high Cu assay.<\/p>\n\n\n\n

    How does fire refining convert scrap into rod-grade melt?<\/h2>\n\n\n\n

    Fire refining converts scrap melt into rod-grade copper by deep oxidation of impurities, slag removal, then controlled reduction so oxygen falls back into the ETP window. Temperature and oxygen \u2014 not furnace brand \u2014 decide whether the rod will draw.<\/p>\n\n\n\n

    \"\"<\/figure>\n\n\n\n

    Engineering sequence used on tilting \/ reverberatory furnaces feeding CCR or Upcast:<\/p>\n\n\n\n

      \n
    1. Charge and melt.<\/strong> Dry, sorted scrap. Wet insulation and oil cause gas porosity and hydrogen later.<\/li>\n\n\n\n
    2. Deep oxidation.<\/strong> Air or oxygen lances raise bath oxygen so Fe, Zn, Sn, Pb, As and Sb oxidize and float as slag. Bath is commonly 1150\u20131200 \u00b0C. Incomplete oxidation leaves Sn\/Zn that re-dissolve in the reduction step.<\/li>\n\n\n\n
    3. Slag-off.<\/strong> Acid or basic flux is selected from the impurity suite. Dirty slag left on the bath recontaminates the next heat.<\/li>\n\n\n\n
    4. Quasi-reduction.<\/strong> Carbonaceous reductant (poling \/ carbon cover) lowers oxygen to the target: \u226410 ppm for OF transfer into Upcast; ~200\u2013400 ppm for ETP CCR. Over-reduction makes a \u201cdead\u201d melt that picks up hydrogen; under-reduction leaves Cu\u2082O networks that crack in drawing.<\/li>\n\n\n\n
    5. Transfer.<\/strong> Covered launder or sealed ladle. Open pouring of refined metal into an Upcast furnace undoes the oxygen work.<\/li>\n<\/ol>\n\n\n\n

      Plant practice summarized by secondary-rod producers is \u201cdeep oxidation, accurate reduction, clean slag.\u201d Zn and Sn that survive oxidation re-enter the metal during reduction and show up as fluctuating Cu% and failed resistivity. Ni and Sb need extra flux time; they are the usual reason a scrap-only heat misses GB\/T 3952 T1 chemistry.<\/p>\n\n\n\n

      For Upcast after refining, the original process is: refining furnace \u2192 sealed transfer of clean liquid \u2192 Upcast 17 mm rod \u2192 cold rolling 17 mm \u2192 8 mm to close as-cast structure and raise mechanical uniformity before breakdown drawing.<\/p>\n\n\n\n

      What process parameters keep 8 mm rod inside ASTM B49 \/ GB\/T 3952?<\/h2>\n\n\n\n

      Qualified 8 mm rod stays inside specification when melt chemistry, oxygen, cast-bar temperature, mill reduction and surface oxide are measured on every coil group \u2014 not only on the first heat of a campaign.<\/p>\n\n\n\n

      Target product window used by mill QA<\/strong><\/p>\n\n\n\n

      Item<\/th>OF Upcast 8 mm<\/th>ETP\/FRHC CCR 8 mm<\/th>Test<\/th><\/tr><\/thead>
      Diameter \/ ovality<\/td>8.00 \u00b10.4 mm class; tighter plant limits common<\/td>8 \u00b10.38 mm typical CC rod table<\/td>Micrometer, 3 axes<\/td><\/tr>
      \u0130letkenlik<\/td>\u2265100\u2013101.4% IACS<\/td>\u2265100% IACS<\/td>Kelvin bridge \/ ASTM B193<\/td><\/tr>
      Resistivity @ 20 \u00b0C<\/td>\u22640.017241 \u03a9\u00b7mm\u00b2\/m (\u22640.01707 for OFE)<\/td>\u22640.017241 \u03a9\u00b7mm\u00b2\/m<\/td>Same<\/td><\/tr>
      Uzama<\/td>\u226530\u201337% (200 mm gauge)<\/td>\u226535% typical CC rod<\/td>Tensile, 200 mm<\/td><\/tr>
      Tensile<\/td>~170\u2013190 N\/mm\u00b2 OF<\/td>~208\u2013260 N\/mm\u00b2 ETP range in mill sheets<\/td>UTM<\/td><\/tr>
      Oxygen<\/td>\u22645\u201310 ppm<\/td>200\u2013350 ppm plant; 100\u2013650 ppm spec<\/td>Inert-gas fusion \/ oxygen analyzer<\/td><\/tr>
      Surface oxide film<\/td>Low; wax optional<\/td>Residual oxide film often <1000 \u00c5 on CC tables<\/td>Oxide-film method GB\/T 3952 App.<\/td><\/tr>
      Coil<\/td>2\u20134 t, ID ~700\u2013900 mm, OD ~1500\u20131800 mm<\/td>3\u20135 t star \/ drop coil<\/td>Weigh + wrap<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

      In-line process numbers that actually move quality<\/strong><\/p>\n\n\n\n