Industrial furnaces, kilns, incinerators and heat-treat equipment operate at 800–1200°C, where ordinary carbon steel and low-alloy steel oxidize rapidly, creep accelerates, and components deform and crack within months. Heat-resistant castings — manufactured from Cr25Ni20, ZG4Cr24Ni48W5Si2 and other heat-resistant steel grades — resist oxidation, creep deformation and thermal fatigue at these temperatures, delivering 10,000–20,000 hours of service life at 1000–1100°C. This guide covers the material grades, components and selection criteria for heat-resistant furnace castings, as part of our broader waste incineration and high-temperature furnace wear-parts program.
What Are Heat-Resistant Furnace Castings and Why Material Matters
Heat-resistant furnace castings are components designed for the interior of industrial furnaces, kilns and incinerators — furnace grate bars, burner nozzles, support beams, kiln furniture and heat-treat baskets. They are continuously exposed to temperatures of 800–1200°C, combined with oxidizing atmospheres, thermal-shock cycling from start-stop operation, and mechanical loads. The failure mode depends on the component: grate bars fail by flame and ash erosion; support beams fail by creep deformation under load; burner nozzles fail by thermal-fatigue cracking. No single alloy is optimal for all duties — the selection problem is matching the alloy’s temperature ceiling, oxidation resistance and creep strength to the specific component and operating temperature.
Heat-Resistant Steel Grades at a Glance
| Kelas | Temp. ceiling | Properti kunci | Komponen umum |
|---|---|---|---|
| ZG304 / ZG316 | ≤ 800 ° C | Biaya rendah, tujuan umum | Low-temp auxiliary parts |
| ZG30Cr18Ni12Si | ≤ 900 ° C | General heat-resistant steel, cost-effective | Grate bars (medium-temp) |
| ZG3Cr18Mn12Si2N | ≤ 950 ° C | Nickel-free, excellent oxidation resistance | Carburizing furnace auxiliaries |
| ZG1Cr25Ni20Si2 | 1000 – 1100 ° C | High-temp strength + creep resistance | Support beams, burner housings |
| ZG4Cr25Ni20Si2 (Cr25Ni20) | 1100 – 1150 ° C | Best creep + oxidation resistance | Grate bars, kiln furniture, support beams |
| ZG4Cr24Ni48W5Si2 | ≥ 1200 ° C | Ultra-high-temp, tungsten-alloyed | Extreme-duty furnace cores |
Density: 7.8–8.0 g/cm³. Tensile strength ≥ 450 MPa, yield strength ≥ 235 MPa (room-temperature reference, GB/T 8492).
ZG30Cr18Ni12Si: The 900°C General-Purpose Grade
ZG30Cr18Ni12Si is the standard heat-resistant steel for medium-temperature furnace components operating at 900°C and below. It offers good oxidation resistance and adequate creep strength for grate bars in medium-temperature kilns and general furnace auxiliary parts. Its advantage is cost-effectiveness — it is the economical choice when operating temperatures do not exceed 900°C. However, above 900°C its oxidation rate accelerates significantly and creep deformation becomes a limiting factor for load-bearing components.
ZG4Cr25Ni20Si2 (Cr25Ni20): The 1100°C Workhorse
ZG4Cr25Ni20Si2 — commonly referred to as Cr25Ni20 — is the optimum grade for components operating at 1000–1150°C. With ~25% chromium and ~20% nickel, it forms a stable protective oxide scale that resists spallation under thermal cycling, and its high nickel content stabilizes the austenitic structure against creep. Compared with ZG30Cr18Ni12Si (900°C-grade), Cr25Ni20 reduces creep rate by over 50% at 1000°C, and its oxidation weight-gain above 1000°C is far lower. This makes it the preferred grade for furnace grate bars, support beams and kiln furniture in high-temperature kilns and incinerators. Service life at 1000–1100°C typically reaches 10,000–20,000 hours.
ZG4Cr24Ni48W5Si2: Ultra-High-Temperature Grade
For furnace cores operating at 1200°C and above, ZG4Cr24Ni48W5Si2 is the extreme-duty grade. With ~48% nickel and tungsten addition, it maintains structural stability and creep resistance where even Cr25Ni20 would degrade. This grade is specified for the most demanding furnace positions — ultra-high-temperature kiln cores, extreme-duty burner assemblies and critical support structures where failure would cause extended downtime. The trade-off is cost: the high nickel and tungsten content makes it significantly more expensive than Cr25Ni20, so it is reserved for positions where the temperature ceiling truly demands it.
Selection Summary by Component and Temperature
- Grate bars (800–1100°C, flame + ash erosion): Cr25Ni20 — oxidation resistance + creep strength + thermal-shock resistance.
- Support beams (1000–1200°C, load-bearing): Cr25Ni20 or ZG4Cr24Ni48W5Si2 for >1150°C — creep is the failure mode, high Ni is essential.
- Burner nozzles (high-temp + thermal cycling): Cr25Ni20 — thermal-fatigue resistance from frequent start-stop cycling.
- Kiln furniture & heat-treat baskets (1000–1100°C): Cr25Ni20 — long service life under repeated thermal cycling.
- Low-temperature auxiliaries (≤ 900°C): ZG30Cr18Ni12Si — cost-effective where high-Ni grades are over-specified.
- Ultra-high-temp furnace cores (≥ 1200°C): ZG4Cr24Ni48W5Si2 — tungsten-alloyed for extreme duty.
Performance vs Standard Heat-Resistant Steel
Compared with standard ZG30Cr18Ni12Si (900°C-grade), the Cr25Ni20 grade extends the temperature ceiling to 1100–1150°C (+200–250°C), reduces creep rate by over 50% at 1000°C, and delivers 10,000–20,000 hours of service life at 1000–1100°C. The top-grade ZG4Cr24Ni48W5Si2 extends the ceiling to 1200°C and beyond — up to +300°C above the 900°C standard. Above 1000°C, oxidation weight-gain is significantly lower, and thermal-fatigue cracking under frequent start-stop cycling is markedly reduced. For any component operating above 1000°C, the Cr25Ni20 grade is not a luxury — it is the difference between a component that lasts years and one that fails in months.
Proses Pengecoran dan Kontrol Kualitas
Heat-resistant castings are produced by lost-foam casting (for complex-structure burner housings and kiln furniture) or sand casting (for grate bars and support beams in larger quantities). 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 to eliminate casting residual stress and stabilize high-temperature performance; different grades use different parameters.
Quality control includes spectroscopic material testing to confirm core elements (Cr, Ni, Si, C) on every piece, high-temperature performance sampling (oxidation weight-gain rate, creep rate), 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 Furnace Castings
Huasuma pengecoran logam capability covers six heat-resistant steel grades spanning the full 800–1200°C temperature range — from ZG304 for low-temperature auxiliaries to ZG4Cr24Ni48W5Si2 for ultra-high-temperature furnace cores. Each component has a grade matched to its operating temperature, not one alloy for all duties. Component structures are optimized by thermodynamic simulation and load analysis — grate-bar airflow channels for combustion efficiency, support-beam cross-sections for creep resistance, burner internal flow-paths for fuel-mixing efficiency. Every piece receives spectroscopic material confirmation and high-temperature performance sampling before shipment. With 30 years of heat-resistant casting experience and multiple batches delivered to Russian furnace operators, this is proven production — not sample trials. ISO 9001 throughout; 24-hour quote response; samples available for in-service validation before bulk orders.
FAQ (Pertanyaan Umum)
What is the best material for furnace grate bars?
For grate bars operating at 800–1100°C with direct flame and ash erosion, ZG4Cr25Ni20Si2 (Cr25Ni20) is the optimum grade — its 25% Cr / 20% Ni content provides oxidation resistance, creep strength and thermal-shock resistance for 10,000–20,000 hours of service at 1000–1100°C.
When should I use ZG4Cr24Ni48W5Si2 instead of Cr25Ni20?
Choose ZG4Cr24Ni48W5Si2 (1200°C+ ultra-high-temp grade) for furnace cores and critical support structures operating above 1150°C, where even Cr25Ni20 would degrade. Its 48% nickel and tungsten addition maintain structural stability at extreme temperatures — but it costs significantly more, so reserve it for positions that truly demand it.
How long do heat-resistant furnace castings last?
Cr25Ni20-grade castings typically deliver 10,000–20,000 hours of service life at 1000–1100°C, depending on operating temperature and grade selection. Above 1100°C, higher-nickel grades (such as ZG4Cr24Ni48W5Si2) are required to maintain comparable life.
What is the temperature ceiling of heat-resistant steel castings?
The temperature ceiling depends on grade: ZG30Cr18Ni12Si is rated for 900°C, ZG4Cr25Ni20Si2 (Cr25Ni20) for 1100–1150°C, and ZG4Cr24Ni48W5Si2 for 1200°C and above. Matching the grade to the operating temperature is the key selection criterion.
Huasuma is a Chinese manufacturer of heat-resistant steel castings (Cr25Ni20, ZG4Cr24Ni48W5Si2, ZG30Cr18Ni12Si and custom high-nickel alloys) for industrial furnaces, kilns, incinerators and heat-treat equipment. Grate bars, burner nozzles, support beams and kiln furniture supplied worldwide. Minta penawaran atau sampel.
