Prilagođeni odljevi teške opreme: Velika ljevaonica u Kini

Heavy equipment castings are structural and functional components produced by pouring molten metal into molds to create parts that combine complex geometries, visoka mehanička čvrstoća, and cost-effective production at scale.

They are indispensable in industries such as construction, rudarstvo, poljoprivreda, rail, marine and energy.

Proper material selection, postupak lijevanja, 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 (Npr., lijevanje pijeska, Izgubljeno-pjegavo lijevanje, casting, centrifugalno lijevanje) intended for structural or functional load-bearing service in mobile or stationary heavy machinery.

Distinctive characteristics

• Veličina & ljestvica. Masses typically range from tens of kilograms (Npr., 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 (savijanje, torzija, axial forces and impact) and therefore require a controlled combination of strength, toughness and stiffness.
  Typical components include booms, okviri, kućište, couplers and hubs.
• Environmental resilience. Designed for exposure to dust, vlaga, korozivne kemikalije (gnojiva, soli),
  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 (tipičan, by application)

• Zatečna čvrstoća (RM): structural cast components: ≥ 400 MPA (common for ductile iron, medium-strength cast steels);
  Komponente visokog stresa (crane hooks, lifting eyes): up to 700–900 MPa for quenched & tempered alloy steels.
• Žilavost utjecaja (Charpy V): odrediti absolute energy at temperature, Npr., ≥ 20 J at −20 °C (quoted as “CVN ≥ 20 J @ −20 °C”), with acceptance according to ASTM E23 / ISO 148.
• Nositi otpor: define either hardness or standardized wear test; Npr., Brinell hardness HB ≥ 200 for abrasion-resistant components, or specify ASTM G65 sand-rubber wheel mass loss limits.
• Dimenzijska stabilnost / tolerancije: large structural castings typically accept ±1–3 mm per metre depending on feature criticality;
  specify tighter tolerances (Npr., ± 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:

• Konstrukcija & earthmoving: kante, prokleti, spojevi, pin housings.
• Rudarstvo: crusher jaws, grinding media, mill housings.
• Poljoprivreda: radne ploče, Kućišta zupčanika, tractor components.
• Šina & transport: spojevi, Komponente kočenja, okviri kamiona.
• Morski & na obali: čvorišta propelera, pumpa, zalihe kormila.
• Stvaranje energije & ulje & plin: Kućišta turbine, tijela ventila, pumpa.

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

• Sivo lijevano željezo (GI)

• • Why used: Izvrsno prigušivanje, good compressive strength, nisko trošak, easy to cast for large complex shapes.
  • Tipične uporabe: Baze stroja, kućište, non-structural covers.
  • Svojstva: Moderate tensile strength, Dobra obradivost, poor ductility/toughness.

• Ductile/Nodular Cast Iron (SG / Duktilno željezo, ASTM A536)

• • Why used: Combination of strength and toughness with lower cost than steel; graphite spheroids give ductility.
  • Tipične uporabe: Spojnice, certain structural castings, zupčanici, mid-duty components.
  • Svojstva: Dobar otpor umora, weldable with caution, responds to austempering (Adi) for higher performance.

• Zbijeno grafitno željezo (CGI)

• • Why used: Between gray and ductile iron—better strength and fatigue than GI, better thermal conductivity than ductile iron.
  • Tipične uporabe: Blokovi motora, medium-stress structural parts where vibration damping plus strength are needed.

• Bijelo željezo & Alloyed White Iron

• • Why used: Izuzetno tvrd i otporan na habanje (often surface hardened by heat treatment), brittle unless alloyed/treated.
  • Tipične uporabe: Mlinarske obloge, crusher jaws, high-abrasion inserts (can be cast as replaceable wear parts).

Cast Steels

• Ugljik & Low-Alloy Cast Steels (Npr., ASTM A216 WCB, A350 L0 etc.)

• • Why used: Higher tensile strength and toughness than irons; better impact and fatigue behavior; weldable and repairable.
  • Tipične uporabe: Strukturalan, kućišta pod pritiskom, crane hooks, highly loaded frames.

• Alloy Cast Steels (Cr-mo, In-cr-i, itd.)

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

Posebne legure & Nehrđajući

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

• • Why used: Otpor korozije (morska voda, kemijsko izlaganje), Dobra duktilnost.
  • Tipične uporabe: Kućiva pumpe, morski dijelovi, corrosive environment structural pieces.

• Dupleks & Super-dupleks (Npr., 2205, 2507 ekvivalenti)

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

• High-nickel & legure otporne na toplinu (Hastelloj, Udruživanje, Legura 20, itd.)

• • Why used: Exceptional corrosion or high-temperature resistance; expensive—used only where necessary.
  • Tipične uporabe: Kemijska obrada, severe corrosive environments, high-temperature housings.

Engineered & Composite Approaches

• Austemperovo duktilno željezo (Adi) - duktilno željezo processed to bainitic matrix (veća snaga + nositi otpor).
• White-iron overlays, tvrdoglav, 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. Procesi lijevanja & Tehnologije

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, površinski završetak, dimenzijska tolerancija, 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.
• Složenost geometrije (podreza, thin webs, Unutarnje šupljine).
• Material family (ferrous vs non-ferrous; nehrđajući, dupleks, Ni-alloys).
• Required mechanical properties (žilavost, umor, wear zones).
• Dimenzijska tolerancija & površinski završetak (as-cast vs finish-machined faces).
• Production volume & jedinični trošak (tooling amortization).
• Inspection and metallurgical cleanliness needs (critical fatigue or pressure zones).
• Ekološki, energy and safety constraints (emisija, rekultivacija pijeska).

Green-sand (conventional sand) lijevanje

• How it works: Patterns press into sand molds bound with clay/organic binders; cores form internal cavities.
• Materijali: Wide range — gray iron, duktilno željezo, lijevanih čelika.
• Jačine: Lowest tooling cost, flexible for very large parts, easy to modify patterns. Ideal for single pieces and low-to-medium volumes.
• Ograničenja: Grubo površinski završetak, larger tolerances, higher porosity risk if gating/riser not optimized.
• Typical scales & metrics: part weights from <10 kg do 100+ tona; surface finish ~Ra 6–20 µm (približno); dimenzijska tolerancija: ±1–5 mm/m (application dependent).
• Prijave: Velika kućišta, mill bases, okviri kamiona, very large pump casings.

Ljuskanje (pijesak obložen smolom) lijevanje

• How it works: Resin-coated sand shells formed on heated patterns; two halves assembled with cores as needed.
• Materijali: Iron and some steels; increasingly used with ductile irons and certain steels.
• Jačine: Better dimensional accuracy and finer surface finish than green sand; thinner sections possible. Good for medium volumes.
• Ograničenja: 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; tolerancije ±0.3–2 mm/m.
• Prijave: Kućišta zupčanika, medium structural castings, parts needing improved finish.

Investicijski lijev (izgubljeni)

• How it works: Wax pattern(s) assembled into tree, ceramic shell built around pattern, wax removed, ceramic shell fired and filled with molten metal.
• Materijali: Feasible for steels and stainless; widely used for non-ferrous (U, Pokrajina, Al); larger castings possible with special setups.
• Jačine: Excellent detail, Fina površinska završna obrada, tanki presjeci, blizu mreže. Low machining.
• Ograničenja: High tooling and process cost; traditionally for small-to-medium parts, though large investicijski 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; tolerancije ±0.05–0.5 mm.
• Prijave: Precizna kućišta, complex stainless parts, components where tight geometry and finish reduce machining.

Izgubljeno-pjegavo lijevanje

• How it works: EPS foam pattern placed in unbonded sand; molten metal vaporizes foam, filling the cavity.
• Materijali: Ferrous and non-ferrous; attractive for near-net shape ferrous parts.
• Jačine: Eliminates cores for complex internal geometry; lower tooling cost vs. ulaganje; good for complex large castings.
• Ograničenja: 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; tolerancije ±0.5–2 mm/m.
• Prijave: Složena kućišta, pump casings with internal passages, automotive and equipment components where cores would be difficult.

Centrifugalno lijevanje

• How it works: Molten metal poured into a rotating mold; centrifugal force distributes metal and minimizes gas/slag entrapment.
• Materijali: Širok raspon; commonly used for irons, čelika, bronze.
• Jačine: Gust, sound castings with good mechanical properties axially (excellent for rings, čahure, rukavi). Low inclusion/porosity.
• Ograničenja: Geometry limited to round/axisymmetric parts; tooling specialized.
• Typical scales & metrics: prstenovi & cylinders from small diameters to multiple metres; excellent internal soundness; tolerancije ±0.1–1 mm depending on finish.
• Prijave: Cylindrical components: bearing sleeves, čahure, cijev, large rings and cylindrical housings.

Permanent-mold & kasting (mostly non-ferrous)

• How it works: Molten metal poured or injected into reusable metal molds (stalni kalupi) or high-pressure die casting.
• Materijali: Mostly non-ferrous (Al, CU legure); some low-pressure permanent molds for certain steels/bronzes.
• Jačine: Izvrsna površinska završna obrada, uske tolerancije, fast cycle times for high volumes.
• Ograničenja: Visoki trošak alata, not typical for very large ferrous heavy-equipment parts.
• Typical scales & metrics: Mali do srednji dijelovi; surface finish Ra 0.4–1.6 µm; tolerancije ±0.05–0.5 mm.
• Prijave: Non-structural housings, components where weight reduction via aluminium is desired.

Kontinuirano lijevanje (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.
• Relevantnost: Quality of upstream feedstocks affects inclusion content and alloy homogeneity for downstream foundries.

5. Toplotna obrada & Thermal Processing

Toplotna obrada is the primary lever foundries and heat-treat shops use to convert as-cast microstructures into the combinations of jačina, žilavost, 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 (Reljef za stres)

• Svrha: Reduce residual stresses from solidification, rough machining or welding.
• Typical cycle: Zagrijati ~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.
• Učinak: Lowers yield of distortion without major microstructure change.

Normaliziranje

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

Ugasiti & temperament (Q&T)

• Svrha: 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: Kuke s dizalicama, 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.

Istočni temperiranje (for ADI — Austempered Ductile Iron)

• Svrha: Produce ausferritic matrix (bainitic ferrite + stabilized carbon in austenite) Za visoku snagu + good ductility/wear resistance.
• Typical cycle: Austenitize (Npr., ~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 (Npr., ronilaca, some wear rails).
• Učinak: ADI attains high Rm (often 700–1100 MPa) with useful ductility; process control and cleanliness are critical.

Žalost (full anneal, spheroidize)

• Svrha: 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.

Rješenje / liječenje otopinom (nehrđajući & dupleks)

• Svrha: Dissolve precipitates and restore corrosion resistance; za dupleks, 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.

Površinsko očvršćivanje & specialized thermal processes

• Indukcijsko otvrdnjavanje, flame hardening, karburizirajući, nitriranje, laser cladding, toplinski sprej — 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)

• Sivo lijevano željezo: obično stress-relief or anneal to stabilize; no Q&T. Use ADI process if higher strength is needed.
• Duktilno željezo: stress-relief or Istočni temperiranje (to make ADI) depending on required Rm/toughness. Ductile irons may be temper-hardened or annealed for machinability.
• Cast Steels (nizak):Normalize for as-cast refinement; ugasiti & temperament Za visoku snagu; Ublažavanje stresa for dimensional control. PWHT may be required for pressure parts.
• Legura (Cr-mo, In-cr-i): Q&T to obtain high strength/toughness; strict control of austenitizing and tempering needed.
• Nehrđajući (austenitski):Rješenje 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.
• Bijelo željezo / High-Cr Iron: obično lijevan for wear; local heat treatment or hardfacing may be preferred to avoid embrittling whole casting.

6. Obrada & 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, izdržljive komponente.

Pre-Machining Preparation — Ensuring Precision

Svrha: Remove defects, Smanjite varijabilnost, and relieve residual stress before formal machining.

Defect Removal & Površinski uvjet

• 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.
• Bljesak & 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: MI (ugljični čelik) or TIG (čelik) welding with matching filler metal; post-weld grinding + MPI inspection.

Preostali ublažavanje stresa

• Toplotna obrada: 600–700 ° C (lijevano željezo) or 800–900°C (čelik), 2–4 h per 25 debljina mm; reduces stress by 60–80%.
• Prirodno starenje: 7–14 days at ambient temperature for ductile iron with low stress requirements.

Core Machining — Targeted Precision

Only critical functional areas (bolt holes, nosiva sjedala, mating surfaces) are precision-machined.

Strukturne komponente (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 & Kuckanje: 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, CBN alati, ±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, Zubi kante)

• Mljevenje: Diamond wheels (120–180 grit), 20–30 m/min, depth ≤0.05 mm.
• Žičana erozija: ±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: otpor korozije (for outdoor/harsh environments), zaštita od nošenja (for abrasive applications), i assembly compatibility (for mating parts).

Corrosion-Resistant Finishes

• Slika: The most common finish for structural castings (Npr., okviri bagera). The process includes:

• • Pre-Treatment: Pucanj (using steel grit, 0.5–1,0 mm) to achieve Sa 2.5 čistoća (Za 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, postizanje 5+ years of corrosion protection in industrial environments.

• Galvaniziranje: Used for cast iron components (Npr., 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 (po ASTM B117).

Wear-Enhancing Finishes

• Tvrdoglav (Weld Overlay): Critical for high-wear areas (Npr., bucket lips, crusher jaws).
  Alloy wires (Npr., Kromov karbid, 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.
• Indukcijsko otvrdnjavanje: Bearing seats and axle journals (Npr., 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

• Maska: For ultra-tight bearing seats (Npr., wind turbine hub bearings), lapping uses abrasive compounds (glinica, 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 (Npr., 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, tehnološki napredak, and global demand:

• Lightweighting: OEMs are replacing cast iron with high-strength steel and aluminum castings to reduce equipment weight (Npr., 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, naprezanje) in castings to monitor real-time performance (Npr., wind turbine hubs with load sensors) enables predictive maintenance, extending service life by 20–30%.

8. Izazovi i rješenja

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

• Large Casting Defects: Shrinkage cavities in thick-walled parts (Npr., 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 (Npr., steel scrap up 20% u 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

Laga offers comprehensive Heavy Equipment Castings services, covering the full process from 3D design, casting simulation, and mold making to large steel casting melting, ulijevanje, toplotna obrada, precizna obrada, and surface protection.

The company produces single castings ranging from 50 kg do 150 tona, serving industries such as construction machinery, rudarska oprema, energija, i morski inženjering.

With multiple process capabilities (lijevanje pijeska, Izgubljeni pjenasti lijevanje, resin sand casting, itd.) and a wide range of materials (ugljični čelik, čelik niskog legura, wear-resistant steel, nehrđajući čelik, and special alloys),

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

Zaključak

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

As digitalization collides with metallurgical science, these components will grow stronger, upaljač, 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