Copper tubes are produced of high phosphorus deoxidized copper, designation Cu-DHP (according to EN 1057) or C12200 (according to ASTM) with guaranteed copper content of 99.90% min. and phosphorus content 0.015-0.040%.
Copper billets
Input material for production of copper tubes is copper billet, DHP quality, dimensions Ø 300 x 540 mm, subject to acceptance test before introduction into production process.
Physical properties of DHP copper |
Specific weight |
8,94 kg/dm³ |
Melting temperature |
1083°C |
Linear expansion coefficient 25-100 ° C |
16,8 · 10 m/m |
Thermal conductivity coefficient at 20 ° C |
340 W/m°K |
Electrical conductivity (approximately) |
42 - 54 S (Ω ) |
Hot press forging of copper billets
 When introduced into production, copper billets (slugs) are heated in induction furnace up to extrusion temperature of 825°C (±25°C).
Copper billets, as input material, are pressed in a horizontal hydraulic press, power 35000kN (i.e. 3500 tons). Throughout the process the pressed copper tubes are submerged in deoxidant-containing water. The given procedure ensures production of perfectly smooth and light surface, free from oxides. Moreover, so obtained tubes with closed ends have absolutely clean internal surface. After the pressing process, tubes are taken out of water and their ends are trimmed. The entire procedure (from start till end) is automatized. Average length of pressed tubes is 15 meters (dimensions of the given tubes are 80 x 10 mm or 113 x 6.50 mm depending on preset parameters).
Cold rolling (pilgering)
Cold rolling of pressed copper tubes is carried out on a triplex pilger mill. This procedure is used to reduce copper tube diameter and wall thickness with minimum material loss.
By the rolling process, with 9-12 mm shift and 72° turn, we obtain, from the input pressed tube, a tube of dimensions 44 x 2 mm, approximately 127 m long.
Extrusion
The very extrusion process takes place on two basic technology lines:
- draw bench technology line
- bull block technology line - finishing machines
Draw bench technology lines are used to manufacture tubes in straight lengths, while bull blocks - finishing machines are used to manufacture tubes in straight lengths, coils, spirals and LW coils.
Extrusion process is used to further reduce tube diameter and wall thickness and to elongate tubes. The given process produces light and shiny surface, exact dimensions - as specified by tolerances (standard). Copper tube transportation (hanging, from floor to floor, ground-based) is fully automatized.
All finishing machines are fitted with eddy current test equipment. Tubes are marked on the finishing machines, mechanically (imprinting) or by ink-printing according to standards or as requested by customer.
Annealing
To produce tubes in a soft or half-hard condition, the tubes are annealed in continuous vacuum bright annealing furnaces.
Annealing is performed in protective atmosphere, in order to eliminate oxidation and ensure clean inner and outer surfaces of the tubes.
Copper tubes are loaded into a basket in which they pass through the entire process at a controlled temperature of 500°C.
Final steps and packaging
Finalization covers:
- straightening tubes from draw benches (on straighteners)
- cutting tubes on saws
- abrasive cleaning and blowing inner surface of the tubes (on VacuBlasts)
- marking (on marking machine according to standards or as requested by customer)
- degreasing
- plasticizing (on extruder)
Packaging process is given special attention
Depending on delivery form and request by the buyer, the manufacture copper tubes are packed in cardboard boxes, on cardboard LW spools, in wooden cases, in bundles protected with PVC foil.
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