Product Overview
ZG40Cr25Ni20Si2 heat-resistant steel radiant tube is a high-performance industrial furnace component engineered for extreme high-temperature applications. Manufactured from high-alloy austenitic heat-resistant cast steel, this product features an integrated support bracket that delivers exceptional oxidation resistance, creep resistance, and thermal shock resistance in demanding thermal processing environments.
As a core component of industrial heating systems, the radiant tube functions as a heat exchanger, transferring thermal energy into the furnace while isolating the high-temperature furnace atmosphere from external systems. The integrated support bracket ensures precise positioning and stable operation of the radiant tube within the furnace, effectively preventing tube deformation and extending service life, even under repeated thermal cycling.
Our ZG40Cr25Ni20Si2 radiant tubes are widely used across various heat treatment production lines in the metallurgical industry, including continuous annealing lines (CAL), continuous galvanizing lines (CGL), and various industrial heating furnaces.
Material Specifications & Chemical Composition
The ZG40Cr25Ni20Si2 material conforms to the Chinese national standard GB/T 8492-2014 for general-purpose heat-resistant steel and alloy castings. It is the equivalent of ASTM HK40 (U.S. standard) and JIS SCH22 (Japanese standard, casting-grade 310S), making it internationally recognized and readily substitutable in global engineering specifications.
Chemical Composition
| Element | Content (%) | Function |
| C | 0.35 – 0.45 | Provides matrix strength and balances toughness |
| Si | 1.5 – 2.5 | Enhances oxidation resistance and refines grain structure |
| Mn | ≤ 2.0 | Improves hot workability |
| P | ≤ 0.04 | Controlled impurity |
| S | ≤ 0.03 | Controlled impurity |
| Cr | 24.0 – 27.0 | Forms protective Cr₂O₃ oxide film for oxidation resistance |
| Ni | 19.0 – 22.0 | Stabilizes austenitic matrix, enhances high-temperature strength |
| Mo | ≤ 0.5 | Optional addition for further strengthening |
Grade Designation Explained
ZG – Cast steel (allows for complex one-piece geometries)
40 – Carbon content of approximately 0.4%
Cr25 – Approximately 25% chromium content
Ni20 – Approximately 20% nickel content
Si2 – Approximately 2% silicon content
Core Performance Characteristics
Extreme High-Temperature Resistance
The ZG40Cr25Ni20Si2 heat-resistant steel delivers outstanding performance at elevated temperatures:
- Long-term service temperature: 1150°C – 1200°C
- Short-term ultimate temperature: 1350°C – 1400°C
- Melting point range: 1323°C – 1370°C
At 1100°C, the high-temperature yield strength maintains approximately 85% of its room-temperature value, far exceeding ordinary stainless steels such as 304 (which has an upper temperature limit of only 800°C).
Superior Oxidation & Corrosion Resistance
The synergistic effect of chromium, nickel, and silicon enables the formation of a dense Cr₂O₃-SiO₂ composite oxide film on the material surface. This protective layer provides:
- Excellent oxidation resistance in oxidizing atmospheres and mildly corrosive environments
- Resistance to sulfidation and carburization in carbon-rich furnace atmospheres
- Resistance to reducing atmospheres (H₂, CO) and oxidizing media (acids, alkalis)
- Resistance to high-temperature sulfides in petrochemical environments, Cl⁻/SO₂ gases generated from waste incineration, and molten glass erosion.
Exceptional Mechanical Strength
- Room-temperature tensile strength: ≥ 550 MPa
- Room-temperature yield strength: ≥ 205 MPa
- Hardness: HB 180 – 220
- Elongation: ≥ 30%
- High-temperature strength (1000°C): ≥ 280 MPa
- High-temperature strength (1100°C): ≥ 220 MPa
- Creep resistance (1100°C / 100MPa / 1000h): Creep ≤ 0.1%
Superior Thermal Fatigue & Thermal Shock Resistance
The austenitic matrix exhibits no phase transformation during thermal cycling, effectively preventing micro-crack formation and extending component life. Key thermal properties include:
- Thermal expansion coefficient: 14.5×10⁻⁶/°C
- Thermal conductivity: 26 W/(m·K)
This combination of low thermal expansion and high thermal conductivity significantly reduces thermal stress concentration risks. In 850°C quenching oil environments, the thermal shock cycle resistance is four times that of ordinary Cr-Mo steels, making it ideal for frequent rapid heating and cooling applications.
Integrated Bracket Design
Our radiant tube with bracket features an integrated support bracket manufactured from compatible heat-resistant materials (ZG40Cr25Ni20 or equivalent). The bracket design offers:
- Secure tube positioning within the furnace through sidewall supporting brackets that secure heating tubes in indirectly heated furnaces
- Stable support that maintains high strength and rigidity at elevated temperatures, preventing deformation or failure
- Thermal expansion compensation – The bracket allows for controlled axial expansion, accommodating furnace thermal gradients
- Reduced thermal stress – Proper support minimizes bending and stress concentration during thermal cycling
- Easy installation and maintenance – Streamlined bracket design facilitates straightforward mounting and replacement
The radiant tube is arranged in the furnace through the furnace wall and radiant-heated via internal combustion or electrical heating elements. The support bracket ensures the tube remains properly aligned throughout its service life, even under extreme thermal and mechanical loads.
Applications
The ZG40Cr25Ni20Si2 heat-resistant steel radiant tube with bracket is extensively used across multiple industries:
- Metallurgical & Heat Treatment
- Petrochemical & Industrial Furnaces
- Power Generation & Energy
- Waste-to-Energy & Environmental
- Specialty Applications
Contact Us
For inquiries, technical specifications, or custom orders for our ZG40Cr25Ni20Si2 heat-resistant steel radiant tube with bracket, please contact our sales team. We welcome discussions on your specific furnace requirements and application conditions to provide the optimal solution for your thermal processing needs.
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