Спеціальні кастинги важкого обладнання: Великий ливарний в Китаї

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

They are indispensable in industries such as construction, видобуток, сільське господарство, rail, marine and energy.

Proper material selection, Процес кастингу, 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 (Напр., пісочний кастинг, Кастинг загубленої панелі, інвестиційне кастинг, відцентрове кастинг) intended for structural or functional load-bearing service in mobile or stationary heavy machinery.

Distinctive characteristics

• Розмір & масштаб. Masses typically range from tens of kilograms (Напр., compact gearbox housings ≈ 50 кг) 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 (згинання, кручення, axial forces and impact) and therefore require a controlled combination of strength, toughness and stiffness.
  Typical components include booms, кадрів, корпус, couplers and hubs.
• Environmental resilience. Designed for exposure to dust, волога, корозійні хімічні речовини (добрива, 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 (типовий, by application)

• Сила на розрив (Rm): structural cast components: ≥ 400 MPA (common for ductile iron, medium-strength cast steels);
  компоненти високого стресу (crane hooks, lifting eyes): up to 700–900 MPa for quenched & tempered alloy steels.
• Вплив міцність (Чарпі V): вказувати absolute energy at temperature, Напр., ≥ 20 J at −20 °C (quoted as “CVN ≥ 20 J @ −20 °C”), with acceptance according to ASTM E23 / ISO 148.
• Опір зносу: define either hardness or standardized wear test; Напр., Brinell hardness HB ≥ 200 for abrasion-resistant components, or specify ASTM G65 sand-rubber wheel mass loss limits.
• Стабільність розмірів / допуски: large structural castings typically accept ±1–3 mm per metre depending on feature criticality;
  specify tighter tolerances (Напр., ± 0,1–0,5 мм) only for precision mounting surfaces after finish machining.

2. Market & Application of Heavy Equipment Castings

Heavy equipment castings serve diverse heavy-duty applications:

• Будівництво & earthmoving: відра, бум, муфти, pin housings.
• Видобуток: crusher jaws, grinding media, mill housings.
• Сільське господарство: ораки, Корпуси передач, tractor components.
• Залізничний & transport: муфти, гальмові компоненти, truck frames.
• Морський & офшорний: гвинтові вузлики, насос кожухів, Рудальні запаси.
• Генерація живлення & нафта & газовий: Турбінні корпуси, Тіла клапана, насос кожухів.

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

• Сірий чавун (GI)

• • Why used: Відмінне демпфірування, good compressive strength, низька вартість, easy to cast for large complex shapes.
  • Типове використання: Машинні бази, корпус, non-structural covers.
  • Властивості: Помірна міцність на розрив, Хороша обробка, poor ductility/toughness.

• Ductile/Nodular Cast Iron (Sg / Пластичне залізо, ASTM A536)

• • Why used: Combination of strength and toughness with lower cost than steel; graphite spheroids give ductility.
  • Типове використання: Муфти, certain structural castings, шестерні, mid-duty components.
  • Властивості: Хороша втома, weldable with caution, responds to austempering (Аді) for higher performance.

• Ущільнене графітове залізо (CGI)

• • Why used: Between gray and ductile iron—better strength and fatigue than GI, better thermal conductivity than ductile iron.
  • Типове використання: Блоки двигуна, medium-stress structural parts where vibration damping plus strength are needed.

• Біла праска & Alloyed White Iron

• • Why used: Надзвичайно жорсткий і зношений (often surface hardened by heat treatment), brittle unless alloyed/treated.
  • Типове використання: Млинні вкладиші, crusher jaws, high-abrasion inserts (can be cast as replaceable wear parts).

Cast Steels

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

• • Why used: Higher tensile strength and toughness than irons; better impact and fatigue behavior; weldable and repairable.
  • Типове використання: Структурний, Корпуси тиску, crane hooks, highly loaded frames.

• Alloy Cast Steels (CR-MO, В CR-i, тощо)

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

Спеціальні сплави & Нержавіючий

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

• • Why used: Корозійна стійкість (морська вода, Хімічна експозиція), Хороша пластичність.
  • Типове використання: Насосні корпуси, Морські частини, corrosive environment structural pieces.

• Дуплекс & Супер-дуплекс (Напр., 2205, 2507 еквіваленти)

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

• High-nickel & Теплостійкі сплави (Хастеллой, Юнель, Сплав 20, тощо)

• • Why used: Exceptional corrosion or high-temperature resistance; expensive—used only where necessary.
  • Типове використання: Хімічна обробка, severe corrosive environments, high-temperature housings.

Engineered & Composite Approaches

• Остемпероване пластичне залізо (Аді) - пластичне залізо processed to bainitic matrix (вища сила + Опір зносу).
• White-iron overlays, твердий, 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. Процеси кастингу & Технології

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, поверхнева обробка, розмірна толерантність, 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.
• Складність геометрії (підрізування, thin webs, Внутрішні порожнини).
• Material family (ferrous vs non-ferrous; нержавіючий, дуплекс, Ni-alloys).
• Required mechanical properties (міцність, втома, wear zones).
• Розмірна толерантність & поверхнева обробка (as-cast vs finish-machined faces).
• Production volume & одинична вартість (tooling amortization).
• Inspection and metallurgical cleanliness needs (critical fatigue or pressure zones).
• Екологічний, energy and safety constraints (викиди, Рекультивація піску).

Green-sand (conventional sand) кастинг

• How it works: Patterns press into sand molds bound with clay/organic binders; cores form internal cavities.
• Матеріали: Wide range — gray iron, пластичне залізо, литі сталі.
• Сильні сторони: Lowest tooling cost, flexible for very large parts, easy to modify patterns. Ideal for single pieces and low-to-medium volumes.
• Обмеження: Грубіша обробка поверхні, larger tolerances, higher porosity risk if gating/riser not optimized.
• Typical scales & metrics: part weights from <10 кг до 100+ тонн; surface finish ~Ra 6–20 µm (блок); розмірна толерантність: ±1–5 mm/m (application dependent).
• Заявки: Великі корпуси, mill bases, truck frames, very large pump casings.

Лиття оболонки (пісок з покриттям смоли) кастинг

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

Лиття по моделлю (Загублений)

• How it works: Wax pattern(s) assembled into tree, ceramic shell built around pattern, wax removed, ceramic shell fired and filled with molten metal.
• Матеріали: Feasible for steels and stainless; widely used for non-ferrous (У, Куточок, Al); larger castings possible with special setups.
• Сильні сторони: Excellent detail, тонке покриття поверхні, тонкі секції, Близька форма. Low machining.
• Обмеження: High tooling and process cost; traditionally for small-to-medium parts, though large інвестиційні кастинги 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; допуски ±0.05–0.5 mm.
• Заявки: Precision housings, complex stainless parts, components where tight geometry and finish reduce machining.

Кастинг загубленої панелі

• How it works: EPS foam pattern placed in unbonded sand; molten metal vaporizes foam, filling the cavity.
• Матеріали: Ferrous and non-ferrous; attractive for near-net shape ferrous parts.
• Сильні сторони: Eliminates cores for complex internal geometry; lower tooling cost vs. інвестиції; good for complex large castings.
• Обмеження: 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; допуски ±0.5–2 mm/m.
• Заявки: Складні корпуси, pump casings with internal passages, automotive and equipment components where cores would be difficult.

Відцентрове кастинг

• How it works: Molten metal poured into a rotating mold; centrifugal force distributes metal and minimizes gas/slag entrapment.
• Матеріали: Широкий асортимент; commonly used for irons, сталей, бронзи.
• Сильні сторони: Густий, sound castings with good mechanical properties axially (excellent for rings, втулки, рукава). Low inclusion/porosity.
• Обмеження: Geometry limited to round/axisymmetric parts; tooling specialized.
• Typical scales & metrics: кільця & cylinders from small diameters to multiple metres; excellent internal soundness; допуски ±0.1–1 mm depending on finish.
• Заявки: Cylindrical components: bearing sleeves, втулки, труба, large rings and cylindrical housings.

Permanent-mold & лиття під тиском (mostly non-ferrous)

• How it works: Molten metal poured or injected into reusable metal molds (Постійні форми) or high-pressure die casting.
• Матеріали: Mostly non-ferrous (Al, Cu сплави); some low-pressure permanent molds for certain steels/bronzes.
• Сильні сторони: Відмінна обробка поверхні, Тісні допуски, fast cycle times for high volumes.
• Обмеження: Висока вартість інструментів, not typical for very large ferrous heavy-equipment parts.
• Typical scales & metrics: дрібні частини; surface finish Ra 0.4–1.6 µm; допуски ±0.05–0.5 mm.
• Заявки: Non-structural housings, components where weight reduction via aluminium is desired.

Безперервний кастинг (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.
• Актуальність: Quality of upstream feedstocks affects inclusion content and alloy homogeneity for downstream foundries.

5. Термічна обробка & Thermal Processing

Термічна обробка is the primary lever foundries and heat-treat shops use to convert as-cast microstructures into the combinations of міцність, міцність, 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 (стрес)

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

Нормалізація

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

Гасіння & вдача (Q&Т)

• Мета: 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: Гачки крана, 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.

Східне загартування (for ADI — Austempered Ductile Iron)

• Мета: Produce ausferritic matrix (bainitic ferrite + stabilized carbon in austenite) for high strength + good ductility/wear resistance.
• Typical cycle: Austenitize (Напр., ~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 (Напр., спонука, some wear rails).
• Ефект: ADI attains high Rm (often 700–1100 MPa) with useful ductility; process control and cleanliness are critical.

Відпал (full anneal, spheroidize)

• Мета: 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.

Рішення відпалити / Лікування розчином (нержавіючий & дуплекс)

• Мета: Dissolve precipitates and restore corrosion resistance; для дуплексу, 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.

Поверхневе затвердіння & specialized thermal processes

• Індукційне твердіння, flame hardening, карбюризація, азотування, laser cladding, тепловий бризок — 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)

• Сірий чавун: зазвичай stress-relief or anneal to stabilize; no Q&Т. Use ADI process if higher strength is needed.
• Пластичне залізо: stress-relief or східне загартування (to make ADI) depending on required Rm/toughness. Ductile irons may be temper-hardened or annealed for machinability.
• Cast Steels (низьколегований):Normalize for as-cast refinement; гасіння & вдача for high strength; полегшення стресу for dimensional control. PWHT may be required for pressure parts.
• Сплави сталей (CR-MO, В CR-i): Q&T to obtain high strength/toughness; strict control of austenitizing and tempering needed.
• Нержавіючий (аустенітний):Рішення відпалити 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.
• Біла праска / High-Cr Iron: зазвичай неухильний for wear; local heat treatment or hardfacing may be preferred to avoid embrittling whole casting.

6. Обробка & 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, довговічні компоненти.

Pre-Machining Preparation — Ensuring Precision

Мета: Remove defects, Зменшити мінливість, and relieve residual stress before formal machining.

Defect Removal & Кондиціонер

• 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.
• Спалах & Burr Grinding: Angle grinders (15–20 kW) or wide-belt sanders (1.2 м) to achieve Ra 25–50 μm, removing inclusions to prevent chatter.
• Crack & Porosity Repair: Я (вуглецева сталь) or TIG (Лепка сталь) welding with matching filler metal; post-weld grinding + MPI inspection.

Залишкова стрес

• Термічна обробка: 600–700 ° C (чавун) or 800–900°C (сталь), 2–4 h per 25 Товщина мм; reduces stress by 60–80%.
• Природне старіння: 7–14 days at ambient temperature for ductile iron with low stress requirements.

Core Machining — Targeted Precision

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

Структурні компоненти (Excavator Booms, Bulldozer Frames)

• Flat Surface Milling: Floor-type boring mills, carbide inserts, flatness ≤0.1 mm/m, РА 6,3-12,5 мкм.
• Hole Drilling & Постукування: 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, Інструменти CBN, ±0.02 mm diameter, roundness ≤0.01 mm, РА 1,6-3,2 мкм.
• Spigot Turning: Coaxiality ≤0.03 mm using live tooling on VTLs.

Wear-Resistant Components (Crusher Liners, Зуби відра)

• Шліфування: Diamond wheels (120–180 крупно), 20–30 m/min, depth ≤0.05 mm.
• Дротова електроерозія: ±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: Корозійна стійкість (for outdoor/harsh environments), Захист зносу (for abrasive applications), і assembly compatibility (for mating parts).

Corrosion-Resistant Finishes

• Малювання: The most common finish for structural castings (Напр., Рамки екскаватора). The process includes:

• • Pre-Treatment: Вибух (using steel grit, 0.5–1,0 мм) to achieve Sa 2.5 чистота (Для 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 мкм, досягнення 5+ years of corrosion protection in industrial environments.

• Гаряче гальванування: Used for cast iron components (Напр., 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 (на ASTM B117).

Wear-Enhancing Finishes

• Твердий (Weld Overlay): Critical for high-wear areas (Напр., bucket lips, crusher jaws).
  Alloy wires (Напр., Карбід хрому, 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.
• Індукційне твердіння: Bearing seats and axle journals (Напр., 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

• Плескіт: For ultra-tight bearing seats (Напр., wind turbine hub bearings), lapping uses abrasive compounds (глинозем, 0.5 мкм) 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 (Напр., excavator lift cylinders) are honed with diamond honing stones, creating a crosshatched surface (РА 0,2-0,4 мкм) 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, Технологічний прогрес, and global demand:

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

8. Виклики та рішення

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

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

Ланге offers comprehensive Heavy Equipment Castings services, covering the full process from 3D design, casting simulation, and mold making to large steel casting melting, заливання, термічна обробка, точна обробка, and surface protection.

The company produces single castings ranging from 50 кг до 150 тонн, serving industries such as construction machinery, гірничодобувне обладнання, енергія, і морська інженерія.

With multiple process capabilities (пісочний кастинг, Загублений кастинг піни, resin sand casting, тощо) and a wide range of materials (вуглецева сталь, Низьколелойська сталь, wear-resistant steel, нержавіюча сталь, and special alloys),

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

Висновок

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

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