1. Ievads
Copper and its alloys occupy a pivotal role in modern industry due to their outstanding electrical conductivity, izturība pret koroziju, un siltuma veiktspēja.
Vēsturiski, civilizations dating back to 5000 BC mastered copper casting in simple stone molds, laying the groundwork for today’s sophisticated techniques.
Šajā rakstā, we explore the full spectrum of copper‑based casting methods, examine their metallurgical principles, and guide engineers in selecting the optimal process for diverse applications.
2. Fundamental Principles of Metal Casting
Every casting method follows four core stages:
- Pelējuma izveide – Technicians form a cavity in sand, metāls, keramikas, or plaster that mirrors the part geometry.
- Izliešana – Furnaces melt copper (kušanas punkts 1 083 ° C) or alloys up to 1 600 ° C, then pour the liquid into molds.
- Sacietēšana – Controlled cooling—guided by thermal conductivity (~ 400 W/m·K for copper) and mold material—drives microstructure development.
- Shake‑Out – Once solid, castings exit the mold and undergo cleaning and post‐processing.
Copper’s high thermal conductivity demands higher mold preheat (200-400 °C) and precise pour control to maintain fluidity (viscosity ~ 6 mPa·s at 1 200 ° C).
Papildus, copper’s termiskā izplešanās (16.5 µm/m·K) requires exact pattern offsets to achieve final dimensions.
3. Major Copper Alloy Casting Methods
Vara and its alloys—brasses, bronzas, copper-nickels, and others—are cast using a range of methods that suit different production volumes, mehāniskās prasības, and dimensional tolerances.
Each technique carries distinct advantages and limitations based on alloy characteristics and desired component outcomes.
This section explores the most prominent copper alloy casting methods in modern manufacturing, along with technical insights to guide process selection.
Smilšu liešana
Procesa pārskats & Aprīkojums
Smilšu liešana remains one of the oldest and most widely used methods for casting copper alloys. It involves packing sand around a reusable pattern inside a mold box.
The sand is bonded with clay (zaļās smiltis) or hardened with chemicals (resin-bonded or CO₂-activated sands). After pattern removal, dobumā ielej izkausētu metālu.
Priekšrocības
- Zemas instrumentu izmaksas, piemērots zemam- līdz vidēja apjoma skrējieniem
- Flexible part sizes—from a few ounces to several tons
- Broad alloy compatibility
Ierobežojumi
- Coarse surface finishes (Ra 6,3-25 µm)
- Loose tolerances (typically ±1.5–3 mm)
- Requires post-casting machining for most precision applications
Ieguldījums (Lost-Wasks) Liešana
Precision Shell Building
Investīciju liešana uses a wax model coated with ceramic slurry to build a thin, high-accuracy shell mold. Pēc izdegšanas, molten metal is poured into the preheated ceramic mold.
Pabalsti
- Lielisks izmēru precizitāte (±0,1–0,3 mm)
- Ideāli piemērots sarežģīts, thin-walled geometries
- Augstāks virsmas apdare (Ra 1,6–3,2 µm)
Izaicinājumi
- Higher tooling costs (due to the need for injection dies)
- Longer cycle times, especially for shell construction and burnout
- Typically economical only for medium-to-high volume ražošanu
Shell Molded Casting
Process Details
Shell molding uses a heated metal pattern coated with resin-bonded sand. When exposed to heat, the resin sets to form a thin shell that acts as the mold.
The process produces more accurate and cleaner castings than traditional sand casting.
Priekšrocības
- Improved surface quality and definition
- Tighter tolerances than green sand molds
- Reduced machining allowance due to near-net shape casting
Ierobežojumi
- Higher material costs (specialized resins and silica sands)
- Expensive pattern tooling (metal patterns required)
Centrbēdze
Horizontal vs. Vertical Setups
Centrbēdzes liešanā, izkausētu metālu ielej rotējošā veidnē, either horizontally or vertically.
The centrifugal force distributes the metal against the mold wall, minimizing porosity and ensuring excellent material integrity.
Galvenās priekšrocības
- High density and reduced porosity—ideal for pressure-retaining components
- Virziena sacietēšana enhances mechanical properties
- Piemērots bukses, gredzeni, caurules, and hollow parts
- Vertical casting often used for small parts; horizontal for large cylinders
Ierobežojumi
- Ierobežots līdz rotācijas simetriskas daļas
- Tooling setup is more complex and costly than static casting
Chill Casting
Sacietēšanas kontrole
Chill casting uses metal molds (often iron or steel) to rapidly extract heat from the molten metal. This rapid solidification refines the grain structure and enhances mechanical properties.
Stiprās puses
- Produces grūtāk, denser castings (līdz 50% increase in hardness vs. smilšu liešana)
- Excellent for phosphor bronze and gunmetal
- Cost-effective for repetitive casting of bars, stieņi, and small parts
Ierobežojumi
- Less suited for sarežģīta ģeometrija
- Limited size range due to mold constraints
Mirkšana (Hot-Chamber and Cold-Chamber)
Pressure Injection Process
Die casting involves injecting molten copper alloys into a high-strength steel mold under high pressure.
Cold-chamber machines are typically used due to the high melting points of copper alloys.
Priekšrocības
- Fast production rates—ideal for mass production
- Superior surface finish and precision (Ra 1–2 µm, tolerances ±0.05 mm)
- Reduces or eliminates machining
Constraints
- Not all copper alloys are suitable (Piem., high zinc brasses can corrode dies)
- Die tooling is dārgi (investment of $50,000 vai vairāk)
- Vislabākais priekš medium to high volumes
Nepārtraukta liešana
Procesa pārskats
Molten metal is poured into a water-cooled mold that continuously forms and pulls solidified metal through a withdrawal system.
Common outputs include rods, bāri, and billets for downstream machining or rolling.
Priekšrocības
- High productivity with minimal human intervention
- Excellent mechanical properties due to controlled solidification
- Smooth surfaces and straightness suitable for automatic feed machining
- Low scrap rate and better yield (pāri 90% materiālu izmantošana)
Tipiski sakausējumi
- Tin bronzes, leaded bronzes, phosphor bronzes, and copper-nickels
Plaster Mould Casting
Specializēta lietošana
This process employs plaster or ceramic molds formed around a pattern to capture fine detail and tight tolerances.
The mold is removed after casting by breaking or dissolving the plaster.
Priekšrocības
- Excellent for sarežģītas formas un gludas virsmas apdares
- Good for prototipus un maza apjoma ražošanu
Trūkumi
- Zema caurlaidība—limits to casting size
- Longer preparation time un limited mold life
Kopsavilkuma salīdzināšanas tabula
| Liešanas metode | Virsmas apdare (Ra) | Izmēru tolerance | Typical Volumes | Galvenās stiprās puses |
|---|---|---|---|---|
| Smilšu liešana | 6.3-25 µm | ±1.5–3 mm | Zema līdz augsta | Zemas izmaksas, alloy flexibility |
| Investīciju liešana | 1.6-3,2 µm | ±0,1–0,3 mm | Vidēja līdz augsta | Augsta precizitāte, sarežģītas daļas |
| Shell Molded Casting | 1.6-3,2 µm | ±0,25–0,5 mm | Vidējs | Stingras pielaides, gatavs automatizācijai |
| Centrbēdze | 3.2-6,3 µm | ±0.25–1.0 mm | Vidējs | Augsts blīvums, minimāli defekti |
| Chill Casting | 3.2-6,3 µm | ±0,5–1,0 mm | Vidējs | Enhanced mechanical properties |
| Mirkšana | 1-2 µm | ± 0,05–0,2 mm | Augsts | Fast cycles, minimal machining |
| Nepārtraukta liešana | 3.2-6,3 µm | ±0.2–0.5 mm/m | Ļoti augsts | Cost-efficient billet production |
| Plaster Mould Casting | 1.6-3,2 µm | ±0,1–0,3 mm | Zema līdz vidēja | Detailed, sarežģītas formas |
4. Common Copper Alloys Used in Casting
Foundries cast a wide array of copper‑based alloys, each engineered to balance mechanical strength, izturība pret koroziju, thermal and electrical performance, un castability.
| Sakausējums | Apzīmējums | Sastāvs (WT%) | Galvenās īpašības | Preferred Casting Methods | Tipiskas lietojumprogrammas |
|---|---|---|---|---|---|
| Brīva mašīna misiņš | C36000 / CZ121 | 61 Cu–35 Zn–3 Pb | Stiepts: 345 MPa Pagarināšana: 20 % Vadītspēja: 29 % IACS |
Smiltis, Ieguldījums, Nomirt, Apvalka formēšana | CNC‑machined fittings, pārnesumi, elektriskie termināli |
| Low‑Lead Brass | C46400 / CZ122 | 60 Cu–39 Zn–1 Pb | Stiepts: 330 MPa Pagarināšana: 15 % NSF‑61 compliant |
Smiltis, Ieguldījums, Nomirt | Potable‑water valves, santehnikas aprīkojums |
| Nesot bronzu | C93200 | 90 Cu–10 Sn | Stiepts: 310 MPa Cietība: HB 90 Lieliska nodilumizturība |
Smiltis, Chill, Centrbēdzes | Bukses, vilces paplāksnes, heavy‑load bearings |
| Alumīnija bronza | C95400 | 88 Cu–9 Al–2 Fe–1 Ni | Stiepts: 450 MPa Cietība: HB 120 Strong seawater corrosion resistance |
Nomirt, Centrbēdzes, Apvalka formēšana | Jūras aparatūra, sūkņa lāpstiņriteņi, vārstu komponenti |
| Fosfora bronza | C51000 | 94.8 Cu–5 Sn–0.2 P | Stiepts: 270 MPa Pagarināšana: 10 % Good fatigue & spring properties |
Ieguldījums, Smiltis, Nomirt | Atsperes, elektriskie kontakti, diaphragms |
Copper‑Nickel (90–10) |
C70600 | 90 Cu–10 Ni | Stiepts: 250 MPa Pagarināšana: 40 % Exceptional biofouling resistance |
Smiltis, Centrbēdzes, Nepārtraukts | Seawater heat‑exchangers, marine piping |
| Copper‑Nickel (70–30) | C71500 | 70 Cu–30 Ni | Stiepts: 300 MPa Superior chloride and erosion resistance |
Smiltis, Nepārtraukts, Centrbēdzes | Condenser tubes, offshore hardware |
| Berilija vara | C17200 | 98 Cu–2 Be | Stiepts: up to 1 400 MPa (vecumā) Vadītspēja: 22 % IACS |
Ieguldījums, Chill, Nomirt | High‑reliability springs, non‑sparking tools, savienotāji |
| Silīcija bronza | C65500 | 95 Cu–5 Si | Stiepts: 310 MPa Corrosion resistant in marine/chemical |
Smiltis, Ieguldījums, Apvalka formēšana | Decorative hardware, kuģu piederumi |
5. Secinājums
Copper and copper‑alloy foundries offer a rich toolbox of casting methods—each balancing maksāt, precizitāte, mehāniskā veiktspēja, un ražošanas apjoms.
By understanding process nuances—from mold materials and thermal management to alloy behavior—engineers can optimize part design, minimize scrap, and ensure reliable performance.
As technologies like additive mold fabrication un real‑time simulation nobriedis, copper casting will continue to evolve, sustaining its critical role in high‑performance manufacturing.
Pie Šis, Mēs ar prieku apspriežam jūsu projekta projektēšanas procesa sākumu, lai nodrošinātu, ka kāds sakausējums ir izvēlēts vai tiek piemērota pēckastā ārstēšana, Rezultāts atbildīs jūsu mehāniskajām un veiktspējas specifikācijām.
Lai apspriestu jūsu prasības, e -pasts [email protected].
FAQ
Can all copper alloys be die-cast?
Ne. Only specific alloys like aluminum bronzes, high-tensile brasses, un silicon brasses are suitable for mirkšana due to the high pressures and rapid cooling involved.
Sakausējumi, piemēram fosfora bronza vai gunmetal are better suited to sand or chill casting.
What’s the difference between centrifugal and chill casting?
- Centrbēdzes liešana uses rotational force to push molten metal into the mold, producing dense, defect-free components (ideal for pipes, bukses, un piedurknes).
- Chill casting uses static metal molds to rapidly solidify the surface, improving mechanical properties and reducing grain size—especially effective for tin bronzes.
Why is continuous casting preferred for high-volume copper alloy bars?
Continuous casting offers consistent quality, lieliskas mehāniskās īpašības, and low scrap rates.
It’s optimal for fosfora bronza, gunmetal, un svina bronza sagataves, especially when integrated with rolling or extrusion processes.
What post-processing is required after casting copper alloys?
Depending on the casting method and alloy, post-processing may include:
- Heat treatment for stress relief or aging (especially for beryllium copper)
- Machining for critical surfaces or tight tolerances
- Surface finishing such as polishing or coating for corrosion protection or aesthetics
