1. Uvod
Copper ranks among humanity’s most versatile metals, thanks to its exceptional electrical conductivity, otpor korozije, i sposobnost oblikovanja.
Štoviše, scientists and engineers rely on copper’s thermal behavior to design components ranging from electrical wiring to heat exchangers.
Stoga, understanding copper’s melting point becomes indispensable in both metallurgy and industrial applications.
2. Definition and Significance of Melting Point
A talište represents the temperature at which a solid transitions into a liquid under equilibrium conditions.
U praksi, it marks the balance between solid-phase bonding forces and thermal agitation.
Stoga, metallurgists use the melting point as a benchmark for selecting materials, designing furnaces, and controlling casting processes.
3. Melting Point of Copper
Pure copper melts at approximately 1,085° C (1,984° F).
At this temperature, copper transitions from a solid to a liquid, allowing it to be cast, joined, or alloyed. In its solid form, copper has a kubik usredotočen na lice (FCC) struktura
4. Thermodynamic and Atomic‑Level Perspective
At the atomic scale, copper’s substantial melting point stems from its metallic bonding—a sea of delocalized electrons gluing positively charged ions.
Its electron configuration, [Ar] 3d¹⁰4s¹, supplies one conduction electron per atom, which not only underpins electrical conductivity but also reinforces interatomic cohesion.
- Enthalpy of fusion: ~13 kJ/mol
- Latent heat of melting: ~205 kJ/kg
These values quantify the energy required to break metallic bonds during melting.
Naduti, copper’s relatively high atomic mass (63.55 amu) and dense FCC lattice (12 nearest neighbors) elevate its bond energy and thermal stability.
5. Factors Affecting Copper’s Melting Point
Several key parameters alter copper’s melting behavior, often by shifting its solid‑to‑liquid transition temperature by tens of degrees Celsius.
Understanding these variables enables precise thermal management in both pure copper processes and alloy production.
Alloying Elements and Impurities
- Zinc and Tin: Introducing 10–40 wt % Zn lowers the melting range to approximately 900–940 °C in brass. Na sličan način, 5–15 wt % Sn yields bronze with a melting interval of 950–1,000 °C.
- Silver and Phosphorus: Even trace silver (≤1 wt %) can raise copper’s liquidus by 5–10 °C, while phosphorus at 0.1 tež % reduces the melting point slightly and improves fluidity.
- Oxygen and Sulfur: Dissolved oxygen forms Cu₂O inclusions above 1,000 ° C, triggering localized melting point depression.
U međuvremenu, sulfur contamination as low as 0.02 tež % leads to embrittlement and creates low‑melting eutectics at grain boundaries.
Grain Size and Microstructure
- Fine vs. Coarse Grains: Fine‑grained copper exhibits a marginally higher melting onset—typically 2–5 °C above coarse‑grained material—because increased grain‑boundary area strengthens the lattice.
- Precipitacijsko otvrdnjavanje: In alloys like Cu–Be, precipitates introduce local strain fields that can elevate melting by up to 8 ° C, depending on precipitate volume fraction.
Crystal Lattice Defects
- Vacancies and Dislocations: High vacancy concentrations (>10⁻⁴ atomic fraction) introduce lattice distortion, lowering the melting point by 3–7 °C.
- Rad na stvrdnjavanju: Cold‑worked copper contains tangled dislocations that reduce cohesive energy, hence depressing melting by about 4 °C compared to annealed copper.
Pressure Effects
- Clausius–Clapeyron Relation: Raising pressure increases the melting temperature at a rate of roughly +3 K per 100 MPA.
Although industrial melts rarely exceed ambient pressure, high‑pressure experiments confirm this predictable slope.
Thermal History and Surface Conditions
- Pre‑heating: Slow pre‑heating to 400–600 °C can outgas surface oxides and moisture, preventing early melting point depression.
- Surface Coatings: Protective fluxes (Npr., borax‑based) form a barrier that stabilizes the surface and maintains the true melting point during open‑air processing.
6. Melting Point of Copper Alloys
Below is a comprehensive list of melting points for a range of common copper alloys.
These values refer to typical liquidus temperatures; alloys often solidify over a range (solidus → liquidus) which we quote here as an approximate melting interval.
| Naziv legure / NAS | Sastav (wt %) | Raspon topljenja (° C) |
|---|---|---|
| C10200 (ECD) | ≥ 99.90 Cu | 1 083 – 1 085 |
| C11000 (Electrolytic Cu) | ≥ 99.90 Cu | 1 083 – 1 085 |
| C23000 (Žuta mjed) | ~ 67 Cu – 33 Zn | 900 – 920 |
| C26000 (Patrona od mjedi) | ~ 70 Cu – 30 Zn | 920 – 940 |
| C36000 (Free‑Machining Brass) | ~ 61 Cu‑38 Zn‑1 Pb | 920 – 940 |
| C46400 (Mornarička mjed) | ~ 60 Cu‑39 Zn‑1 Sn | 910 – 960 |
| C51000 (Fosforna bronca) | ~ 95 Cu‑5 Sn | 1 000 – 1 050 |
| C52100 (High‑Strength Phos. Bronza) | ~ 94 Cu‑6 Sn | 1 000 – 1 050 |
| C61400 (Aluminijska bronca) | ~ 82 Cu‑10 Al‑8 Fe | 1 015 – 1 035 |
| C95400 (Aluminijska bronca) | ~ 79 Cu‑10 Al‑6 Ni‑3 Fe | 1 020 – 1 045 |
| C83600 (Leaded Red Brass) | ~ 84 Cu‑6 Sn‑5 Pb‑5 Zn | 890 – 940 |
| C90500 (Gun Metal) | ~ 88 Cu‑10 Sn‑2 Zn | 900 – 950 |
| C93200 (Silicon Bronze) | ~ 95 Cu‑3 Si‑2 Mn | 1 000 – 1 050 |
| C70600 (90–10 Cupronickel) | 90 Cu‑10 Ni | 1 050 – 1 150 |
| C71500 (70–30 Cupronickel) | 70 Cu‑30 Ni | 1 200 – 1 300 |
| C17200 (Beryllium Copper) | ~ 97 Cu‑2 Be‑1 Co | 865 – 1 000 |
7. Melting Point Variation in Copper Alloys
Copper’s melting behavior shifts dramatically once alloying elements enter the lattice.
U praksi, metallurgists exploit these variations to tailor casting temperatures, fluidnost, i mehanička izvedba.
Influence of Alloying Elements
- Cinkov (Zn):
Adding 10–40 wt % Zn to form brass lowers the melting range to roughly 900–940 °C, thanks to the Cu–Zn eutectic at ~39 wt % Zn (melting at ~900 °C).
High‑zinc brasses (iznad 35 % Zn) begin to approach that eutectic composition, exhibiting a narrower melting interval and superior fluidity. - Kositar (Sn):
Introducing 5–15 wt % Sn yields bronze with a melting interval of 950–1,000 °C.
Here, the Cu–Sn phase diagram shows a eutectic at ~8 wt % Sn (~875 °C), but practical bronze compositions lie above that, pushing the liquidus near 1,000 °C to ensure adequate strength. - Nikla (U):
In cupronickels (10–30 wt % U), the liquidus climbs from 1,050 ° C (za 10 % U) do 1,200 ° C (za 30 % U).
Nickel’s strong affinity for copper raises the bond energy and shifts both solidus and liquidus upward. - Aluminij (Al):
Aluminum bronzes (5–11 wt % Al) melt between 1,020–1,050 °C.
Their phase diagram reveals complex intermetallic phases; a primary eutectic around 10 % Al occurs at ~1,010 °C, but higher‑Al alloys require temperatures above 1,040 °C to fully liquefy. - Beryllium (Be):
Even small additions (~2 wt %) of Be reduce the melting interval to 865–1,000 °C by promoting a low‑temperature eutectic near 2 % Be (~780 °C).
This facilitates precision work but demands careful health‑and‑safety controls during melting.
Eutectic and Solid‑Solution Effects
- Eutectic Systems: Alloys at or near eutectic compositions solidify at a single, sharp temperature—ideal for die casting or thin‑wall castings.
Na primjer, a Cu–Zn alloy at 39 % Zn solidifies at 900 ° C, maximizing fluidity. - Solid Solutions: Sub‑eutectic or hypo‑eutectic alloys exhibit a melting range (solidus to liquidus).
Wider ranges can cause “mushy” zones during solidification, risking segregation and porosity. Za razliku od, hyper‑eutectic alloys may form brittle intermetallics upon cooling.
8. Industrial Relevance of the Melting Point of Copper
Copper’s melting point of 1 085 ° C (1 984 ° F) plays a pivotal role in virtually every large‑scale operation that transforms ore into finished components.
U praksi, manufacturers leverage this property to optimize energy use, control product quality, and minimize waste.
Smelting and Refining
Foundries and smelters routinely heat copper concentrates to 1 200–1 300 ° C, exceeding the metal’s melting point to ensure complete slag separation.
By maintaining the furnace at roughly 1 100 ° C, operators reduce oxidation losses: well‑controlled processes can cut dross formation from 4 % down to under 1 %.
Naduti, electrorefining plants bypass remelting by dissolving impure anodes in acidic solutions, yet they still depend on initial melts to cast high‑purity plates.
Casting and Alloy Production
When producing brass, bronza, or aluminum bronze, technicians set melt temperatures just above each alloy’s tekućina.
Na primjer, 70/30 brass melts at about 920 ° C, dok 6 % aluminum bronze requires 1 040 ° C.
By holding the bath within a narrow ±5 °C window, they achieve full mold penetration, reduce porosity by up to 30 %, and ensure consistent alloy chemistry.
Atmosphere Control and Oxidation Management
Because molten copper reacts vigorously with oxygen, many facilities retrofit induction or reverberatory furnaces with argon or nitrogen shrouds.
These inert environments lower oxidation losses from 2 % (open‑air) do u nastavku 0.5 %, thereby improving surface finish and electrical conductivity for critical components like bus bars and connectors.
Recycling and Energy Efficiency
Recycling scrap copper consumes do 85 % less energy than primary production.
Međutim, mixed-alloy scrap often contains brasses and bronzes with liquidus points ranging from 900 °C do 1 050 ° C.
Modern scrap melting systems employ regenerative burners and waste‑heat recovery, trimming overall energy use by 15–20 %.
Kao rezultat, secondary copper now contributes over 30 % of the global supply, driven by cost savings and environmental advantages.
9. Applications Requiring Precise Melting Control
Certain manufacturing processes demand exceptionally tight temperature regulation around copper’s melting point to guarantee quality, performanse, and repeatability.
Ispod, we examine three key applications that hinge on precise melting control.
Casting
U casting, foundries maintain melt temperatures within ±5 °C of the alloy’s liquidus to ensure smooth mold filling and minimize porosity.
Na primjer, when casting a phosphor‑bronze impeller (liquidus ~1,000 °C), operators typically hold the bath at 1,005 ° C.
By doing so, they achieve full mold penetration without overheating, which would otherwise degrade dimensional accuracy and increase dross formation.
High‑Purity Copper Production for Electrical Use
Manufacturers of electrical-grade copper (≥ 99.99 % Pokrajina) perform melting under vacuum or inert gas, controlling temperature to within ±2 °C od 1,083 ° C.
This stringent control prevents gas entrapment and contamination, both of which compromise conductivity.
Štoviše, tight thermal management in continuous casting lines yields fine grain structures that further enhance electrical performance and reduce resistivity below 1.67 µΩ·cm.
Additive Manufacturing and Thin‑Film Deposition
In laser powder‑bed fusion (LPBF) of copper alloys, engineers adjust laser power and scan speed to produce localized melt pools at around 1,100 - 1,150 ° C.
Precise thermal profiling—often monitored in real time with pyrometers—prevents balling, poroznost, and keyhole defects.
Na sličan način, in physical vapor deposition (PVD) of copper films, crucible temperatures must stay within ±1 °C of the evaporation setpoint (tipično 1,300 ° C) to control deposition rates and film uniformity down to nanometer precision.
10. Comparisons with Other Metals
Comparing copper’s melting point to a broader spectrum of metals further clarifies how atomic structure and bonding energies dictate thermal behavior—and helps engineers select appropriate materials.
Melting Points and Bond Energies
| Metal | Talište (° C) | Bond Energy (kJ/mol) | Kristalna struktura |
|---|---|---|---|
| Magnezij | 650 | 75 | HCP |
| Cinkov | 420 | 115 | HCP |
| Dovesti | 327 | 94 | FCC |
| Aluminij | 660 | 106 | FCC |
| Srebro | 961 | 216 | FCC |
| Zlato | 1 064 | 226 | FCC |
| Bakar | 1 085 | 201 | FCC |
| Kobalt | 1 495 | 243 | HCP (α‑Co) |
| Nikla | 1 455 | 273 | FCC |
| Titanijum | 1 668 | 243 | HCP (α‑Ti) |
| Željezo | 1 538 | 272 | BCC (δ‑Fe), FCC (γ‑Fe) |
| Platina | 1 768 | 315 | FCC |
| Volfram | 3 422 | 820 | BCC |
Implications for Alloy Design
- Energy and Cost: Metals like copper strike a balance between reasonable melting temperatures (oko 1 085 ° C) and strong mechanical properties.
Za razliku od, processing tungsten or platinum requires specialized high‑temperature equipment and greater energy input. - Joining and Castability: When combining dissimilar metals, such as brazing copper to titanium,
engineers select fillers with melting points below the lower‑temperature metal to avoid base‑metal damage. - Performance Tuning: Alloy designers leverage these melting and bonding trends to engineer materials that perform under specific thermal conditions,
whether they need a low‑temperature fusible alloy or a high‑temperature superalloy.
11. Zaključak
The melting point of copper and copper alloys epitomizes a balance between strong metallic bonding and workable thermal requirements.
Engineers achieve optimal performance in smelting, lijevanje, and advanced manufacturing by controlling impurities, legirajući elementi, and process parameters.
As industries strive for greater energy efficiency and material sustainability, a thorough grasp of copper’s melting behavior remains a critical foundation for innovation.
Česta pitanja
How is the melting point of copper measured?
Laboratories determine copper’s melting point using differential scanning calorimetry (DSC) or a high‑temperature furnace equipped with calibrated thermocouples.
These methods heat samples at controlled rates (typically 5–10 °C/min) and record the onset of the solid‑to‑liquid transition.
What impurities most strongly affect copper’s melting point?
Zinc and tin significantly lower copper’s liquidus (to 900–940 °C in brasses and 950–1,000 °C in bronzes). Obrnuto, trace silver can raise it by 5–10 °C.
Oxygen and sulfur often form low‑melting oxides or sulfides, causing localized melting‑point depressions.
