Peças fundidas de equipamentos pesados personalizados: Grande fundição na China

As peças fundidas de equipamentos pesados são componentes estruturais e funcionais produzidos por derramamento de metal fundido em moldes para criar peças que combinam geometrias complexas, alta resistência mecânica, e produção econômica em escala.

They are indispensable in industries such as construction, mineração, agricultura, rail, marine and energy.

Proper material selection, processo de fundição, thermal and mechanical post-processing, and rigorous quality control determine service life and lifecycle cost.

1. What are Heavy Equipment Castings

Heavy-equipment castings are near-net-shape metallic components produced by casting processes (Por exemplo, fundição de areia, Castamento de cravo perdido, elenco de investimento, elenco centrífugo) intended for structural or functional load-bearing service in mobile or stationary heavy machinery.

Distinctive characteristics

• Tamanho & escala. Masses typically range from tens of kilograms (Por exemplo, compact gearbox housings ≈ 50 kg) up to many tonnes (large mining truck frames and mill housings — tens to hundreds of tonnes).
  Linear dimensions commonly exceed several metres for large assemblies.
• Load-bearing function. These parts transmit static and dynamic loads (flexão, torção, axial forces and impact) and therefore require a controlled combination of strength, toughness and stiffness.
  Typical components include booms, quadros, caixas, couplers and hubs.
• Environmental resilience. Designed for exposure to dust, umidade, corrosive chemicals (fertilizantes, salts),
  abrasives and broad temperature ranges (example service window: −40 °C to +150 ° c; extremes may require specialized alloys or surface protection).
• Design trade-off — cost vs durability. Castings often cost more to produce per part than simple fabricated weldments but provide integrated geometry,
  fewer assemblies and elimination of weld crotches (common crack initiation sites), resulting in longer field life and lower total cost of ownership for many heavy-duty applications.

Representative performance targets (típico, by application)

• Resistência à tracção (Rm): structural cast components: ≥ 400 MPA (common for ductile iron, medium-strength cast steels);
  Componentes de alto estresse (crane hooks, lifting eyes): up to 700–900 MPa for quenched & tempered alloy steels.
• Tenacidade de impacto (Charpy v): especificar absolute energy at temperature, Por exemplo, ≥ 20 J at −20 °C (quoted as “CVN ≥ 20 J @ −20 °C”), with acceptance according to ASTM E23 / ISO 148.
• Resistência ao desgaste: define either hardness or standardized wear test; Por exemplo, Brinell hardness HB ≥ 200 for abrasion-resistant components, or specify ASTM G65 sand-rubber wheel mass loss limits.
• Estabilidade dimensional / tolerâncias: large structural castings typically accept ±1–3 mm per metre depending on feature criticality;
  specify tighter tolerances (Por exemplo, ± 0,1-0,5 mm) only for precision mounting surfaces after finish machining.

2. Market & Application of Heavy Equipment Castings

Heavy equipment castings serve diverse heavy-duty applications:

• Construção & earthmoving: baldes, booms, acopladores, pin housings.
• Mineração: crusher jaws, grinding media, mill housings.
• Agricultura: arados, Altas de equipamento, tractor components.
• Trilho & transport: acopladores, componentes de freio, quadros de caminhão.
• Marinho & offshore: Hubs de hélice, carcaças da bomba, estoques de leme.
• Geração de energia & óleo & gás: Capas de turbinas, corpos da válvula, carcaças da bomba.

Each sector imposes distinct requirements: wear resistance and impact toughness in mining; corrosion resistance in marine; fatigue endurance in rail; and tight tolerances and smooth finishes in hydraulic and rotating equipment.

3. Common Materials Selection — Heavy-Equipment Castings

Cast Irons

• Ferro fundido cinza (GI)

• • Why used: Excelente amortecimento, good compressive strength, baixo custo, easy to cast for large complex shapes.
  • Usos típicos: Bases de máquinas, caixas, non-structural covers.
  • Propriedades: Força de tração moderada, boa máquinabilidade, poor ductility/toughness.

• Ductile/Nodular Cast Iron (Sg / Ferro dúctil, ASTM A536)

• • Why used: Combination of strength and toughness with lower cost than steel; graphite spheroids give ductility.
  • Usos típicos: Acoplamentos, certain structural castings, engrenagens, mid-duty components.
  • Propriedades: Boa resistência à fadiga, weldable with caution, responds to austempering (Adi) for higher performance.

• Ferro de grafite compactado (CGI)

• • Why used: Between gray and ductile iron—better strength and fatigue than GI, better thermal conductivity than ductile iron.
  • Usos típicos: Blocos do motor, medium-stress structural parts where vibration damping plus strength are needed.

• Ferro branco & Alloyed White Iron

• • Why used: Extremamente difícil e resistente ao desgaste (often surface hardened by heat treatment), brittle unless alloyed/treated.
  • Usos típicos: Forros de moinho, crusher jaws, high-abrasion inserts (can be cast as replaceable wear parts).

Cast Steels

• Carbono & Low-Alloy Cast Steels (Por exemplo, ASTM A216 WCB, A350 L0 etc.)

• • Why used: Higher tensile strength and toughness than irons; better impact and fatigue behavior; weldable and repairable.
  • Usos típicos: Estrutural, caixas de pressão, crane hooks, highly loaded frames.

• Alloy Cast Steels (Cr-Mo, In-Cr-i, etc.)

• • Why used: Tailored for high strength, elevated temperature, wear or impact resistance. Heat treatable to high strength/toughness combinations.
  • Usos típicos: Extinto & tempered components in high-stress applications.

Ligas especiais & Inoxidável

• Austenitic and Ferritic Stainless Castings (CF8/CF8M, ASTM A351 / A743)

• • Why used: Resistência à corrosão (água do mar, exposição química), boa ductilidade.
  • Usos típicos: Altas da bomba, peças marinhas, corrosive environment structural pieces.

• Duplex & Super-duplex (Por exemplo, 2205, 2507 equivalentes)

• • Why used: Higher strength than austenitic stainless and superior resistance to chloride stress-corrosion cracking; used when corrosion + strength are required.
  • Usos típicos: Seawater equipment, offshore components.

• High-nickel & ligas resistentes ao calor (Hastelloy, Inconel, Liga 20, etc.)

• • Why used: Exceptional corrosion or high-temperature resistance; expensive—used only where necessary.
  • Usos típicos: Processamento químico, severe corrosive environments, high-temperature housings.

Engineered & Composite Approaches

• Ferro dúctil austempered (Adi) - Ferro dúctil processed to bainitic matrix (maior força + resistência ao desgaste).
• White-iron overlays, HardFacing, ceramic/metallic linings — used to give wear zones very high abrasion resistance while keeping the bulk casting tougher and cheaper.
• Functionally graded or bimetal castings — combine tough base metal with hard surface alloys or replaceable wear inserts.

Typical mechanical property ranges — illustrative table

Values are indicative. Final design must use certified MTR/test data and supplier-specific heat-treatment results.

4. Processos de fundição & Tecnologias

Selecting the right casting process is among the earliest and most consequential choices in producing heavy-equipment components.

The choice determines achievable geometry, metallurgical quality, acabamento superficial, tolerância dimensional, tooling cost and lead time — and it strongly influences downstream needs for heat treatment, machining and NDT.

key process drivers

When choosing a casting route, weigh these primary drivers:

• Part size and weight (kg → tonnes), and whether one piece is required or several assemblies.
• Complexidade da geometria (Undercuts, thin webs, Cavidades internas).
• Material family (ferrous vs non-ferrous; inoxidável, duplex, Ni-alloys).
• Required mechanical properties (resistência, fadiga, wear zones).
• Tolerância dimensional & acabamento superficial (as-cast vs finish-machined faces).
• Production volume & Custo unitário (tooling amortization).
• Inspection and metallurgical cleanliness needs (critical fatigue or pressure zones).
• Ambiental, energy and safety constraints (emissões, Recuperação de areia).

Green-sand (conventional sand) elenco

• How it works: Patterns press into sand molds bound with clay/organic binders; cores form internal cavities.
• Materiais: Wide range — gray iron, Ferro dúctil, aços fundidos.
• Pontos fortes: Lowest tooling cost, flexible for very large parts, easy to modify patterns. Ideal for single pieces and low-to-medium volumes.
• Limitações: Coarser surface finish, larger tolerances, higher porosity risk if gating/riser not optimized.
• Typical scales & metrics: part weights from <10 kg para 100+ toneladas; surface finish ~Ra 6–20 µm (aprox); tolerância dimensional: ±1–5 mm/m (application dependent).
• Aplicações: Grandes caixas, mill bases, quadros de caminhão, very large pump casings.

Moldagem por concha (Areia revestida de resina) elenco

• How it works: Resin-coated sand shells formed on heated patterns; two halves assembled with cores as needed.
• Materiais: Iron and some steels; increasingly used with ductile irons and certain steels.
• Pontos fortes: Better dimensional accuracy and finer surface finish than green sand; thinner sections possible. Good for medium volumes.
• Limitações: Higher tooling cost than green sand; lower maximum size than green sand.
• Typical scales & metrics: part weights up to a few tonnes; surface finish ~Ra 1–6 µm; tolerâncias ±0.3–2 mm/m.
• Aplicações: Altas de equipamento, medium structural castings, parts needing improved finish.

Fundição de investimento (Lost Wax)

• How it works: Wax pattern(s) assembled into tree, ceramic shell built around pattern, wax removed, ceramic shell fired and filled with molten metal.
• Materiais: Feasible for steels and stainless; widely used for non-ferrous (Em, Cu, Al); larger castings possible with special setups.
• Pontos fortes: Excellent detail, Acabamento da superfície fina, Seções finas, forma próxima da rede. Low machining.
• Limitações: High tooling and process cost; traditionally for small-to-medium parts, though large peças fundidas de investimento are possible with special equipment.
• Typical scales & metrics: weights from a few grams to a few tonnes; surface finish ~Ra 0.4–1.6 µm; tolerâncias ±0.05–0.5 mm.
• Aplicações: Estados de precisão, complex stainless parts, components where tight geometry and finish reduce machining.

Castamento de cravo perdido

• How it works: EPS foam pattern placed in unbonded sand; molten metal vaporizes foam, filling the cavity.
• Materiais: Ferrous and non-ferrous; attractive for near-net shape ferrous parts.
• Pontos fortes: Eliminates cores for complex internal geometry; lower tooling cost vs. investimento; good for complex large castings.
• Limitações: Process control needed to prevent gas defects; surface finish and tolerance depend on sand compaction.
• Typical scales & metrics: medium-to-large parts (tens to thousands kg); surface finish similar to sand casting ~Ra 2–10 µm; tolerâncias ±0.5–2 mm/m.
• Aplicações: Caixas complexas, pump casings with internal passages, automotive and equipment components where cores would be difficult.

Elenco centrífugo

• How it works: Molten metal poured into a rotating mold; centrifugal force distributes metal and minimizes gas/slag entrapment.
• Materiais: Ampla gama; commonly used for irons, Aça, bronzes.
• Pontos fortes: Denso, sound castings with good mechanical properties axially (excellent for rings, buchas, mangas). Low inclusion/porosity.
• Limitações: Geometry limited to round/axisymmetric parts; tooling specialized.
• Typical scales & metrics: anéis & cylinders from small diameters to multiple metres; excellent internal soundness; tolerâncias ±0.1–1 mm depending on finish.
• Aplicações: Cylindrical components: bearing sleeves, buchas, cano, large rings and cylindrical housings.

Permanent-mold & morrer de elenco (mostly non-ferrous)

• How it works: Molten metal poured or injected into reusable metal molds (Moldes permanentes) or high-pressure die casting.
• Materiais: Mostly non-ferrous (Al, Ligas de cu); some low-pressure permanent molds for certain steels/bronzes.
• Pontos fortes: Excelente acabamento superficial, tolerâncias apertadas, fast cycle times for high volumes.
• Limitações: Alto custo de ferramentas, not typical for very large ferrous heavy-equipment parts.
• Typical scales & metrics: peças pequenas a médicas; surface finish Ra 0.4–1.6 µm; tolerâncias ±0.05–0.5 mm.
• Aplicações: Non-structural housings, components where weight reduction via aluminium is desired.

Fundição contínua (upstream feed)

• How it works: Produces billets/slabs for downstream forging/machining; not a finishing process for actual heavy components but relevant to material supply.
• Relevância: Quality of upstream feedstocks affects inclusion content and alloy homogeneity for downstream foundries.

5. Tratamento térmico & Thermal Processing

Tratamento térmico is the primary lever foundries and heat-treat shops use to convert as-cast microstructures into the combinations of força, resistência, wear resistance and dimensional stability required by heavy-equipment castings.

Common heat-treatment processes and when to use them

Temperatures and times below are typical engineering ranges. Final cycles must be validated for the specific alloy, section size and part geometry and recorded in the supplier’s process sheet.

Stress-relief anneal (Reliefamento do estresse)

• Propósito: Reduce residual stresses from solidification, rough machining or welding.
• Typical cycle: Aquecer para ~500–700 °C, hold to equalize (time depends on section thickness), slow cool.
• When used: Standard after heavy rough machining or multi-pass welding; before finish machining for dimensional stability.
• Efeito: Lowers yield of distortion without major microstructure change.

Normalização

• Propósito: Refine coarse as-cast grain and homogenize the matrix to improve toughness and prepare for subsequent tempering/quench.
• Typical cycle: Aquecer para ~850–980 °C (above austenitizing for steels), air-cool to refine grain.
• When used: Cast steels prior to quench & temperamento, or when cast microstructure is coarse.
• Efeito: Produces finer, more uniform ferrite/pearlite microstructure and dimensional stabilization.

Querece & temperamento (Q&T)

• Propósito: Produce high strength plus toughness for high-stress or fatigue-critical components.
• Typical cycle: Austenitize ~840–950 °C depending on alloy → quench (oil/water/polymer or gas) → temper ~450–650 °C to achieve required toughness/hardness.
• When used: Ganchos de guindaste, high-stress frames, safety-critical forged/cast steels requiring Rm >> 600 MPA.
• Critical controls: Quench severity and part fixturing to avoid cracking/distortion; tempering schedule tailored to balance hardness vs toughness.

Temelagem oriental (for ADI — Austempered Ductile Iron)

• Propósito: Produce ausferritic matrix (bainitic ferrite + stabilized carbon in austenite) for high strength + good ductility/wear resistance.
• Typical cycle: Austenitize (Por exemplo, ~900–950 °C) → quench to austempering bath at 250–400 °C and hold until transformation completed → cool.
• When used: Wear components requiring a combination of toughness and wear resistance (Por exemplo, Impellers, some wear rails).
• Efeito: ADI attains high Rm (often 700–1100 MPa) with useful ductility; process control and cleanliness are critical.

Recozimento (full anneal, spheroidize)

• Propósito: Soften for machinability (spheroidize), relieve stresses, or restore ductility after high-temperature processing.
• Typical cycle: Heat to subcritical or low austenitizing temperatures (depends on alloy) and hold long times; controlled slow cooling.
• When used: To ease machining of hard as-cast white irons or high-carbon steels, or to produce spheroidized carbides.

Recozimento da solução / tratamento de solução (inoxidável & duplex)

• Propósito: Dissolve precipitates and restore corrosion resistance; para duplex, achieve balanced austenite/ferrite.
• Typical cycle:900–1150 ° C. (material dependent) → rapid cooling (quench/water) to avoid sigma phase or carbide precipitation.
• When used: Stainless castings and duplex parts after casting/welding. Requires strict control to avoid sensitization.

Endurecimento da superfície & specialized thermal processes

• Endurecimento de indução, flame hardening, carburismo, nitretagem, laser cladding, Spray térmico — used when wear resistance is needed only at specific local zones.
• Salt baths / molten salt quench historically used (especially for austempering); environmental and handling considerations may favor fluidized beds or gas quenching alternatives.

Process selection by material family (practical guidance)

• Ferro fundido cinza: geralmente stress-relief or anneal to stabilize; no Q&T. Use ADI process if higher strength is needed.
• Ferro dúctil: stress-relief or Temelagem oriental (to make ADI) depending on required Rm/toughness. Ductile irons may be temper-hardened or annealed for machinability.
• Cast Steels (baixa liga):Normalize for as-cast refinement; Querece & temperamento for high strength; alívio do estresse for dimensional control. PWHT may be required for pressure parts.
• Aços de liga (Cr-Mo, In-Cr-i): Q&T to obtain high strength/toughness; strict control of austenitizing and tempering needed.
• Inoxidável (austenítico):Recozimento da solução and controlled quench to maintain corrosion resistance; avoid tempering ranges that cause sensitization.
• Duplex Stainless: solution anneal at specified temperature followed by rapid cooling to preserve duplex balance; require controlled cooling to avoid sigma phase.
• Ferro branco / High-Cr Iron: geralmente como fundido for wear; local heat treatment or hardfacing may be preferred to avoid embrittling whole casting.

6. Usinagem & Finish Operations — Heavy-Equipment Castings

Heavy-equipment castings—from 50 kg tractor transmission housings to 150-ton mining truck frames—require specialized machining and finish operations to transform rough castings into functional, componentes duráveis.

Pre-Machining Preparation — Ensuring Precision

Propósito: Remove defects, reduzir a variabilidade, and relieve residual stress before formal machining.

Defect Removal & Condicionamento da superfície

• Riser/Gate Removal: Flame cutting (oxy-acetylene, ~3100°C) for carbon steel/cast iron; carbon arc gouging (30–50 V) for alloy steels. Target ≤2 mm transition step to avoid stress risers.
• Clarão & Burr Grinding: Angle grinders (15–20 kW) or wide-belt sanders (1.2 m) to achieve Ra 25–50 μm, removing inclusions to prevent chatter.
• Crack & Porosity Repair: MEU (aço carbono) or TIG (liga de aço) welding with matching filler metal; post-weld grinding + MPI inspection.

Alívio do estresse residual

• Tratamento térmico: 600–700 ° C. (ferro fundido) or 800–900°C (aço), 2–4 h per 25 mm espessura; reduces stress by 60–80%.
• Envelhecimento natural: 7–14 days at ambient temperature for ductile iron with low stress requirements.

Core Machining — Targeted Precision

Only critical functional areas (bolt holes, assentos de rolamento, mating surfaces) are precision-machined.

Componentes estruturais (Excavator Booms, Bulldozer Frames)

• Flat Surface Milling: Floor-type boring mills, carbide inserts, flatness ≤0.1 mm/m, RA 6,3-12,5 μm.
• Hole Drilling & Tocando: M20–M60 with internal coolant drills, TiN-coated HSS-E taps, ISO 6H threads.

Transmission/Drive Components (Gearbox & Axle Housings)

• Bearing Seat Boring: Ø200–500 mm, Ferramentas CBN, ±0.02 mm diameter, roundness ≤0.01 mm, RA 1.6-3,2 μm.
• Spigot Turning: Coaxiality ≤0.03 mm using live tooling on VTLs.

Wear-Resistant Components (Crusher Liners, Dentes do balde)

• Moagem: Diamond wheels (120–180 Grit), 20–30 m/min, depth ≤0.05 mm.
• Fio EDM: ±0.01 mm tolerance, stress-free machining for complex shapes.

Tooling Selection — Material Compatibility

Surface Finish Operations: Enhancing Durability & Compatibility

Surface finishing for heavy-equipment castings serves three core purposes: Resistência à corrosão (for outdoor/harsh environments), desgaste de proteção (for abrasive applications), e assembly compatibility (for mating parts).

Corrosion-Resistant Finishes

• Pintura: The most common finish for structural castings (Por exemplo, quadros de escavadeira). The process includes:

• • Pre-Treatment: Tiro jateando (using steel grit, 0.5–1,0 mm) to achieve Sa 2.5 limpeza (para ISO 8501-1) and a surface profile of 50–80 μm for paint adhesion.
  • Primer: Epoxy primer (60–80 μm dry film thickness, DFT) for corrosion barrier.
  • Topcoat: Polyurethane topcoat (80–120 μm DFT) for UV resistance. Total system DFT: 140–200 μm, alcançando 5+ years of corrosion protection in industrial environments.

• Galvanização a quente: Used for cast iron components (Por exemplo, agricultural tractor parts) exposed to salt or chemicals.
  Castings are dipped in molten zinc (450° c) to form a 80–120 μm zinc-iron alloy layer, providing salt spray resistance ≥500 hours (por ASTM B117).

Wear-Enhancing Finishes

• HardFacing (Weld Overlay): Critical for high-wear areas (Por exemplo, bucket lips, crusher jaws).
  Alloy wires (Por exemplo, Carboneto de cromo, Cr₃C₂) are deposited via MIG welding, creating a 3–5 mm thick layer with HB 550–650. This extends wear life by 3–5× vs. uncoated cast steel.
• Endurecimento de indução: Bearing seats and axle journals (Por exemplo, mining truck axles) are heated via induction coils (20–50 kHz) to 850–900°C,
  then quenched, creating a 2–4 mm deep martensitic layer with HRC 50–55. This improves surface hardness while retaining core toughness.

Precision Surface Finishes

• Laping: For ultra-tight bearing seats (Por exemplo, wind turbine hub bearings), lapping uses abrasive compounds (alumina, 0.5 μm) and a rotating lap plate
  to achieve surface finish Ra 0.025–0.05 μm and flatness ≤0.005 mm—critical for minimizing bearing noise and extending service life.
• Honing: Hydraulic cylinder bores (Por exemplo, excavator lift cylinders) are honed with diamond honing stones, creating a crosshatched surface (RA 0,2-0,4 μm) that retains oil, reducing friction and improving seal performance.

7. Market Trends and Future Directions

The heavy equipment casting industry is evolving to meet sustainability goals, Avanços tecnológicos, and global demand:

• Lightweighting: OEMs are replacing cast iron with high-strength steel and aluminum castings to reduce equipment weight (Por exemplo, 10–15% lighter excavators), cutting fuel consumption by 5–8%.
• Green Manufacturing: Foundries are adopting low-emission melting (electric arc furnaces vs. coke-fired cupolas) and recycling scrap (90% of cast iron scrap is recycled, reducing CO₂ emissions by 30%).
• Smart Castings: Embedding sensors (temperatura, variedade) in castings to monitor real-time performance (Por exemplo, wind turbine hubs with load sensors) enables predictive maintenance, extending service life by 20–30%.

8. Desafios e soluções

Heavy equipment casting faces persistent challenges, with innovative solutions emerging to address them:

• Large Casting Defects: Shrinkage cavities in thick-walled parts (Por exemplo, 100 mm mining truck frames) are mitigated via simulation software (optimizing riser design) and sequential pouring (filling the mold in stages).
• Cost Pressure: Rising raw material prices (Por exemplo, steel scrap up 20% em 2024) are offset by modular casting designs (combining 2–3 welded parts into one casting) and 3D-printed molds (reducing tooling costs by 40%).
• Skilled Labor Shortage: Automated pouring systems (robotic ladles) and AI-powered NDT (machine learning to detect defects) are replacing manual labor, improving consistency and reducing reliance on skilled workers.

Choose LangHe for Heavy Equipment Castings

LangHe offers comprehensive Heavy Equipment Castings services, covering the full process from 3D design, casting simulation, and mold making to large steel casting melting, derramando, tratamento térmico, usinagem de precisão, and surface protection.

The company produces single castings ranging from 50 kg para 150 toneladas, serving industries such as construction machinery, Equipamento de mineração, energia, e engenharia marinha.

With multiple process capabilities (fundição de areia, lançamento de espuma perdida, resin sand casting, etc.) and a wide range of materials (aço carbono, Aço de baixa liga, wear-resistant steel, aço inoxidável, and special alloys),

LangHe provides strict quality assurance through chemical composition analysis, testes não destrutivos (UT/RT/MT/PT), and dimensional inspection to meet ASTM, EM, and ISO standards, ensuring long-term reliability under the most demanding operating conditions.

Conclusão

Heavy equipment castings embody a paradox—massive yet precise, traditional yet high-tech.

As digitalization collides with metallurgical science, these components will grow stronger, isqueiro, and more sustainable.

The industry’s future lies not in abandoning casting, but in elevating it through physics-based modeling and closed-loop material flows.

When the next generation of mining shovels digs deeper or wind turbines reach higher, their cast hearts will beat with algorithmic intelligence and ecological responsibility.

 

“We shape iron; then iron shapes the world.”

— Foundry proverb inscribed on the Gates of the American Foundry Society