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High-Strength Brass
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Dezincification-Resistance Brass
Lead-Free Brass
Stainless Steel
Carbon Steel
Specialty Metals
Raw Materials
Copper is obtained from copper ore and copper scraps. There are three kinds of copper ore; sulfide ore, oxide ore and natural copper. Natural and oxide ores are the secondary products of sulfide ore, which is 65% of the whole amount of copper ore. Most of the sulfide copper ore is processed into copper by pyrometallurgical process. As the sulfide copper ore isn't reduced as it is, the ore is first processed into 30-50% Matte in blast, reverberatory or flash furnace and then copper anode with 98% purity in converter. Finally, electrolytic copper with higher than 99.99% purity from the copper anode through electrolytic refining process.
Raw materials for the production of copper and copper alloy has two categories; ingot of electrolytic copper or zinc and scrap . There are three types of scrap; bulk materials obtained from manufacturing process, chips generated at machining process and waste materials. Mixing these scraps with electrolytic copper or zinc ingot and then melting and casting the mixed materials produces copper alloy. Therefore, industry of copper alloy is recycling industry, that is, environment-friendly industry. Copper as the primary material and secondary additive elements such as zinc, lead, tin and nickel are mixed, melted and cast into ingots and billets. These billets are then produced into plate, rod, tube, bar and wire through rolling, extrusion or drawing process.
Materials Chips Scraps Pure copper Electrolytic zinc Others
Proportion 42% 35% 10% 8% 5%
Crucible or low frequency induction furnaces are mainly used in melting copper and copper alloy. While gas absorption during the brass melting does nor matter, the loss amount of evaporated Zn, which is resulted from its low melting point, is critical Therefore more filter equipment has to be applied, and the filtered dust, which is usually composed of 40-60 percent of oxidized zinc, are required to be re-used. Low frequency induction furnace is divided into two types: crucible and channel types.
Item Chips Scraps
Structure Fundamental Structure Change Available
Heating and Melting Chamber Unit Type Seperate Type
Furnace / Output Capacity 6 / 3.5 ton, 7.5 / 3.5 ton 8 / 3.5 ton
Life 3 ~ 6 months 12 ~ 24 months
Remained Melt Unnecissary Necessary
Workability Discontinuous Continuous
Composition Change Easy Difficult
Stirring Power Strong Weak
Scrap Type Chip or Cluster Cluster
The coiled crucible is heated by supplying electric current through the coil to melt metal. Cold material can be used in this type of furnace. This type is suited to small quantity batch production but its thermal efficiency is lower than channel type. Unit type of heating chamber shortens its life. Since remained melt is not necessary, it is easy to change composition and work discontinues operation. Stirring primarily occurs at the middle point of the coil where tesla is highest Therefore, input flux is compressed on crucible wall, causing decrease in wear resistance of refractory, oxidation of melt and rolling of oxide compound. Strong stirring power enables small cutting chips to be used in this type of furnace.
Metal is melted by making a ring at the point corresponding to the second coil of single phase AC transformer and supplying current through the first coil. The second current is induced in the metal to be heated and melted. Low frequency of 50-60 Hz is used. This type has higher capacity than the crucible type. It is easy to change the structure. Heating and melting chamber is separate type. The capacity of electric power is unlimited and the life of the furnace is 1-2 years. Since remained melt is required for the next operation, continuous melting with little change of composition is possible. Scrap of cluster type is used due to the weaker stirring power.
Casting is an intermediate process to produce ingots for semi-manufactured goods or casting materials for final products. Ingot, which is different from casting, is processed by plastic working such as extrusion or rolling to produce bar, wire and plate. Continuous casting process, by which a large amount of production and quality improvement are feasible, is primarily used for the production of copper and its alloy. Continuous casting process is divided into the following two types; vertical continuous casting (VCC) and horizontal continuous casting (HCC).
Enquipment Configuration Furnace-casting machine Furnace-holding furnace-casting machine-withdrawing machine-cutter
Operation Discontinuous Continuous
Material Change Easy Removal of changed part
Production Type Job shop type production, small batch production Few items production, mass production
The number of Casting Bars 2 ~ 4 strand 1 ~ 3 strand
Mold Copper mold Copper + graphite mold
Cooling System Mold, spray and water bath cooling Mold and spray cooling
Casting Bar Withdrawer Self-weight type by cylinder Self-load type by pinch roll
Billet Surface Good Good or surface trimming
Vertical continuous casting is divided into two types; full continuous and semi-continuous casting process. Full continuous casting machine is used for the production of oxygen free copper and copper alloy. The semi-continuous casting machine produces copper alloy ingots and consists of furnace-holding furnace-casting machine or furnace-casting machine. Full continuous casting process is used for mass production. Semi-continuous casting process is suitable for job shop type and small batch production. The furnaces used in the former and latter processes are shaft or inductive melting furnace with a large capacity and crucible type inductive melting furnace, respectively.
Using the magnetic lubricant property and thermal conductivity of graphite, Ingots are withdrawn from the graphite mold, which is directly cooled under the holding furnace to produce bar, wire, plate and tube. Equipment of this method consists of furnace-holding furnace-casting machine-withdrawer-cutter, like that of vertical continuous casting. Crucible inductive furnace, which is suitable for mass production, is primarily used. The production of bars and tubes needs little cutting process.
Extrusion is the process to extrude material in a container through a mold hole to produce an article with desired shape and smaller cross section area. This process is used for hot working of non-ferrous metals. As billet is highly compressed in the container and die, it is widely used for the processing of high temperature materials with low workability. The simple working process and high extruding pressure increase the density of extruded products and improve the mechanical properties. There are two types of extrusion methods; direct extrusion in which the direction of pressure is identical with that of extrusion and indirect extrusion by which the product is extruded in the opposite direction of the pressure.
  Direct Extrusion Indirect Extrusion
Equipment Configuration Simple, general process Complex, repair difficult
Extrusion Direction Parallel to progress direction of stem Opposite to progress direction of stem
Friction High friction and energy loss Low energy loss
Dead Zone Large Small
Billet Oxidation Layer High inner mixing input Low metal flow, minimum defects
Defect Piping defect inevitable Skin cover
Shell Thickness 1 ~ 2 mm 1 ~ 2 mm
Discard Length 20% of billet diameter 10% of billet diameter
Piping Remove Length Rear part, 2~3% of whole length -
Production Yield 80 % 92 %
The principle of this method, which is also called forward extrusion, is to squeeze a toothpaste tube. The high friction between the billet and the wall of a container increases the ram load. The piping defects occur at the center or other inner part in the rear section of an extruded product, accordingly depreciation its value. To remove this defected part, rear part of the extruded bar is discarded, lowering the production yield. The temperature difference between the first and latter stage results in the variation of mechanical properties. To minimize this effect, gradient heating is applied or cooling process after extrusion is modified.
In this method, which is also called backward extrusion, a die moves forward billet or a container with the billet moves while stem fixing the die is immovable. Therefore, the friction between the billet and the wall of a container is very low. Moreover, energy consumption for extrusion and working temperature are low. It is fit for large amount of production. The uniform metal flow restricts the occurrence of defects and increases the production yield. The homogenous microstructure of a product extruded by this method proves the reliability and improves mechanical properties. On the other hand, intricate equipment is required and extruded products are likely to be stained with oxidation layer accumulated on the die surface. Advanced technologies to keep the billet temperature constant and to seal the billet are required.