Grinding components in cement mills and power-plant coal mills operate in high-temperature, abrasive environments where ordinary carbon-steel and low-alloy-steel liners lose strength and oxidize rapidly, leading to early thinning, deformation and failure. Heat-resistant grinding components — manufactured from Cr25Ni20 (ZG4Cr25Ni20Si2) and nickel-based alloys — maintain stable high-temperature strength, resist oxidation and resist abrasive wear at temperatures up to 1150°C (with nickel-based alloys extending to 1200°C and above), delivering 1.5–2 times the wear life of ordinary steel components at 300°C and above. This guide covers material selection and performance for heat-resistant mill components, as part of our broader power generation, cement grinding and powder processing wear-parts program. For mill internals, see our вкладиш кульового млина стр.
What Are Heat-Resistant Grinding Components and Why Material Matters
Heat-resistant grinding components are the liners, partition plates, discharge grates and wear parts inside cement mills and power-plant coal mills. In cement mills, the hot-air inlet section reaches 300–350°C. In power-plant coal mills (medium-speed mills and fan mills), the hot-air inlet reaches 300–400°C and the grinding zone reaches 100–200°C. At these temperatures, ordinary carbon-steel and low-alloy-steel liners suffer strength degradation and accelerated oxidation — under the combined action of high temperature and abrasive particle wear, they thin rapidly, leading to declining mill efficiency and frequent shutdowns for replacement. Material selection determines whether a liner lasts 6–12 months or 1.5–2 times longer.
Material Grades for Heat-Resistant Grinding Components
| Grade | Температура стелі | Ключова властивість | Типовий компонент |
|---|---|---|---|
| ЗГ304 / ЗГ316 | ≤ 800 ° C | Низька вартість, універсального призначення | Допоміжні деталі для низьких температур |
| ZG30Cr18Ni12Si | ≤ 900 ° C | Загальна жароміцна сталь | Medium-temp liners |
| ZG3Cr18Mn12Si2N | ≤ 950 ° C | Без нікелю, відмінна стійкість до окислення | Oxidizing-environment liners |
| ZG1Cr25Ni20Si2 | 1000-1100 ° С | Міцність за високих температур + стійкість до повзучості | High-temp liners |
| ZG4Cr25Ni20Si2 (Cr25Ni20) | 1100-1150 ° С | Best creep + oxidation + wear resistance | Hot-air inlet liners, grates |
| Сплав на основі нікелю | ≥ 1200°C | Ultra-high-temp, specialized | Specialized mill extreme-duty |
Density: 7.8–8.0 g/cm³. Tensile strength ≥ 450 MPa, yield strength ≥ 235 MPa (room-temperature reference). Casting: lost-foam (complex structures) and sand casting (standard liners). Pouring temperature: 1530–1570°C.
ZG30Cr18Ni12Si: The 900°C Baseline
ZG30Cr18Ni12Si is the standard heat-resistant steel for medium-temperature mill components operating at 900°C and below. It offers adequate oxidation resistance and creep strength for general-duty liners. However, in cement mill hot-air inlet sections and power-plant coal mill hot-air sections where temperatures reach 300–400°C, ordinary low-alloy steel liners suffer combined high-temperature oxidation and abrasive wear — in power-plant coal mills, ordinary liners typically last only 6–12 months. ZG30Cr18Ni12Si represents the minimum threshold for heat-resistant service; below it, carbon steel is inadequate for sustained high-temperature grinding duty.
ZG4Cr25Ni20Si2 (Cr25Ni20): The Workhorse for Hot-Air Inlet Sections
ZG4Cr25Ni20Si2 — commonly referred to as Cr25Ni20 — is the optimum grade for grinding components operating at elevated temperatures. With ~25% chromium and ~20% nickel, it maintains stable high-temperature strength where ordinary low-alloy steel weakens, and forms a stable protective oxide scale that resists oxidation. In cement mill hot-air inlet sections (300–350°C) and power-plant coal mill hot-air sections (300–400°C), Cr25Ni20 liners maintain strength and wear resistance at temperature, extending service life to 1.5–2 times that of ordinary low-alloy steel components under the same conditions. High-temperature oxidation weight-gain is significantly lower than carbon and low-alloy steel. For any grinding component in the hot-air path, Cr25Ni20 is the grade that prevents premature thinning and unplanned shutdowns.
Nickel-Based Alloys: Ultra-High-Temperature Specialized Grade
For specialized mill components operating at 1200°C and above — extreme-duty positions in specialized equipment — nickel-based alloys provide the highest temperature capability. These alloys maintain structural stability and creep resistance where even Cr25Ni20 would degrade. Nickel-based alloy components are specified for the most demanding positions where the specific alloy grade and operating conditions must be confirmed against the actual duty. The trade-off is cost: nickel-based alloys are significantly more expensive than Cr25Ni20, so they are reserved for positions where the temperature ceiling truly demands it.
Performance vs Standard Low-Alloy Steel Components
Compared with ordinary low-alloy steel grinding components (rated for 400°C and below), Cr25Ni20 components extend the temperature ceiling to 1100–1150°C — a dramatic expansion of the usable temperature range. At 300°C and above, the strength degradation rate of Cr25Ni20 is far lower than ordinary low-alloy steel, which loses strength rapidly as temperature rises. High-temperature oxidation weight-gain is far lower than carbon and low-alloy steel, meaning the component does not thin prematurely from oxidation. The combined effect: 1.5–2 times the wear life at 300°C and above, reducing shutdown frequency and maintenance cost. In power-plant coal mills where ordinary steel liners last only 6–12 months, Cr25Ni20 liners significantly extend this interval — the difference between an annual maintenance shutdown and a multi-year service interval.
Selection Summary by Mill Type and Temperature
- Cement mill hot-air inlet liners (300–350°C): Cr25Ni20 — stable high-temp strength + oxidation resistance + abrasive wear resistance, 1.5–2x life vs ordinary steel.
- Power-plant coal mill hot-air section (300–400°C): Cr25Ni20 — replaces ordinary steel liners that last only 6–12 months.
- Coal mill grinding zone (100–200°C): ZG30Cr18Ni12Si — adequate for the lower temperature zone, cost-effective.
- Partition plates and discharge grates (high-temp + wear): Cr25Ni20 — strength stability + wear resistance in combined duty.
- Medium-temp liners (≤ 900°C): ZG30Cr18Ni12Si — cost-effective where Cr25Ni20 is over-specified.
- Ultra-high-temp specialized positions (≥ 1200°C): Nickel-based alloy — confirm specific alloy grade against operating conditions.
Процес лиття та контроль якості
Heat-resistant grinding components are produced by lost-foam casting (for complex structures) or sand casting (for standard liners). Pouring temperature is 1530–1570°C. A pre-pour “double rule” — furnace-front temperature measurement plus sample-block chemistry check — ensures chemical composition meets specification before pouring. Heat treatment consists of solution treatment plus stabilization for heat-resistant steel grades, eliminating casting residual stress and stabilizing high-temperature performance; nickel-based alloys use dedicated heat-treatment parameters.
Quality control includes spectroscopic material testing to confirm core elements (Cr, Ni, Si, C) on every piece, high-temperature performance sampling, and dimensional tolerance verification — all fully traceable. ISO 9001 quality system throughout; material and test reports available. Supports GOST compliance requirements.
Why Huasuma for Heat-Resistant Grinding Components
Хуасуми металеве лиття capability covers six heat-resistant steel and alloy grades spanning the full 800–1200°C temperature range — from ZG304 for low-temperature sections to nickel-based alloys for ultra-high-temperature specialized positions. Each component has a grade matched to its operating temperature and wear characteristics, not one alloy for all duties. Lost-foam casting produces complex-structure components in one piece, eliminating welded-joint weak points that would fail under high-temperature service. Every piece receives spectroscopic material confirmation before shipment, with the pre-pour double rule ensuring composition compliance at the furnace front. With 30 years of heat-resistant casting experience and multiple batches delivered to Russian mill operators, this is proven production. ISO 9001 throughout; 24-hour quote response; samples available for in-service validation before bulk orders.
FAQ
What is the best material for cement mill hot-air inlet liners?
For cement mill hot-air inlet liners operating at 300–350°C, ZG4Cr25Ni20Si2 (Cr25Ni20) is the optimum grade — its 25% Cr / 20% Ni content maintains stable high-temperature strength and oxidation resistance under abrasive wear, delivering 1.5–2 times the service life of ordinary low-alloy steel liners.
How long do heat-resistant grinding components last?
Cr25Ni20 grinding components typically deliver 1.5–2 times the wear life of ordinary low-alloy steel components at 300°C and above, depending on operating conditions. In power-plant coal mills, ordinary steel liners last 6–12 months; Cr25Ni20 liners significantly extend this interval, reducing shutdown frequency and maintenance cost.
What is the temperature ceiling of heat-resistant grinding components?
The temperature ceiling depends on grade: ZG30Cr18Ni12Si is rated for 900°C, ZG4Cr25Ni20Si2 (Cr25Ni20) for 1100–1150°C, and nickel-based alloys for 1200°C and above. In cement and coal mill service, the hot-air inlet (300–400°C) and grinding zone (100–200°C) are the primary temperature considerations.
When should I use nickel-based alloys instead of Cr25Ni20?
Nickel-based alloys are specified for specialized mill positions operating at 1200°C and above, where even Cr25Ni20 would degrade. The specific alloy grade must be confirmed against the actual operating conditions. Due to significantly higher cost, nickel-based alloys are reserved for positions where the temperature ceiling truly demands it.
Huasuma is a Chinese manufacturer of heat-resistant grinding components (Cr25Ni20, nickel-based alloys, ZG30Cr18Ni12Si and custom high-nickel alloys) for cement mills, power-plant coal mills and high-temperature grinding equipment. Liners, partition plates, discharge grates and wear parts supplied worldwide. Запит цінової пропозиції або зразка.
