Product Advantage Summary
In modern power generation, especially in circulating fluidized bed (CFB) boilers, the air cap (also referred to as air nozzle or bubble cap) is a critical component installed on the air distribution plate. It is responsible for uniformly distributing primary air into the furnace to fluidize the bed material and sustain stable combustion. Operating continuously in an extremely harsh environment characterized by high-temperature oxidation at 900–1000°C and severe coal ash erosion, conventional alloys often fail prematurely due to wear, deformation, and cracking.
Our customized boiler air caps manufactured from ZG40Cr25Ni20Si2 (equivalent to ASTM A297 HK40 / EN 1.4848) are specifically engineered to address this challenge. This high-chromium, high-nickel austenitic heat-resistant cast steel delivers exceptional performance in power plant CFB boilers, waste-to-energy (WtE) facilities, biomass co-firing plants, and petrochemical fluidized bed reactors. We offer a comprehensive range of configurations, including bell-type, directional "7"-type, bi-directional "A"-type, and multi-directional flow designs, all fully customizable based on client-provided drawings and site-specific operational parameters.
Material Specifications & Technical Data
ZG40Cr25Ni20Si2 is a premium austenitic heat-resistant cast steel manufactured in strict compliance with GB/T 8492-2014 (Chinese National Standard for Heat-Resistant Steel and Alloy Castings for General Applications).
Chemical Composition (wt%)：
| Element | Content Range | Primary Function |
| C | 0.35–0.45 | Provides high-temperature strength and hardness; balances strength and toughness |
| Cr | 24.0–26.0 | Forms a dense Cr₂O₃ protective oxide film; core contributor to oxidation resistance |
| Ni | 19.0–21.0 | Stabilizes the austenitic matrix; enhances high-temperature toughness and creep resistance |
| Si | 1.5–2.5 | Strengthens the compactness of the oxide film; improves oxidation and carburization resistance |
| Mn | ≤1.5 | Optimizes casting fluidity; reduces internal defects |
| P/S | ≤0.035 | Strict impurity control for high toughness and structural integrity |
International Grade Equivalents：
- USA： ASTM A297 HK40
- EU / Germany： EN 10295 / DIN 17465 - 1.4864 (X15CrNiSi25‑20) / GX40CrNiSi25‑20
- Japan： JIS G5122 SCH22
- ISO： GX40NiCrSi25-20
Key Product Features & Performance Advantages
Exceptional High-Temperature Strength & Creep Resistance
ZG40Cr25Ni20Si2 maintains a stable austenitic structure up to 1200°C. At 900–1000°C operating temperatures, it retains over 85% of room-temperature strength with creep rate ≤0.5% after 1000 hours under load, effectively preventing air cap sagging or deformation during prolonged service.
01
Superior Oxidation & Corrosion Resistance
High chromium (~25%) and silicon (~2%) content promotes a dense, self-healing Cr₂O₃–SiO₂ oxide film. This barrier resists oxidation and corrosive flue gas attack in coal and waste-to-energy boilers, maintaining an oxidation rate below 0.1 mm/year at 1100°C without spalling.
02
Outstanding Thermal Fatigue Resistance
Subjected to frequent CFB boiler start-stop cycles, ZG40Cr25Ni20Si2 exhibits thermal shock life up to 4 times that of Cr-Mo steels. It retains over 85% strength after 1000 thermal cycles, leveraging austenitic toughness to prevent cracking under repeated thermal stress.
03
High Hardness & Wear Resistance
This alloy provides significantly greater high-temperature hardness than 316 stainless or Cr28Ni4 grades. It effectively withstands severe particle erosion and ash impingement in fluidized bed combustion, directly mitigating premature wear failure and extending component service life.
04
Precision Casting & Structural Integrity
Manufactured via investment or EPC casting for near-net-shape precision, our air caps feature porosity-free structures and superior surface finish. Rigorous post-cast solution heat treatment relieves stress and optimizes microstructure, eliminating leakage risks inherent in welded assemblies.
05
Mechanical Properties (Representative Values)：
| Parameter | Value | Condition |
| Tensile Strength (Room Temp) | ≥550 MPa | As-cast + heat treated |
| Tensile Strength (1000°C) | ≥280 MPa | High-temperature service |
| Tensile Strength (1100°C) | ≥400 MPa | Short-term high temperature |
| Yield Strength | ≥250 MPa | Room temperature |
| Elongation | ≥30% | Room temperature |
| 1000h Creep Rate | ≤0.5% | At 1200°C under load |
| Oxidation Rate | <0.1 mm / year | Continuous use at 1150°C |
| Maximum Service Temperature | 1100–1200°C | Long-term operation |
Application Scenarios
Our ZG40Cr25Ni20Si2 air caps are deployed across a wide spectrum of high-temperature industrial applications：
- Power Generation Plants： CFB boiler air distribution plate air caps, slag cooler nozzles, and loop seal return nozzles for coal-fired, coal gangue, and biomass co-firing units.
- Waste-to-Energy (WtE) Facilities： Corrosion-resistant air caps for municipal solid waste (MSW) incineration boilers, where flue gases contain aggressive Cl⁻ and SO₂ compounds.
- Petrochemical Industry： Fluidized bed reactor air distributors and high-temperature burner nozzles.
- Metallurgical & Heat Treatment： Furnace components requiring high creep strength and oxidation resistance, including radiant tubes, furnace rollers, and heat treatment fixtures.
Company Advantages
Proven Expertise in Heat-Resistant Alloy Casting
We possess extensive manufacturing experience in ZG40Cr25Ni20Si2 components-including furnace trays, radiant tubes, heat treatment baskets, and high-temperature fixtures-which provides a solid metallurgical and process foundation for every boiler air cap project. Our long-standing production of HK40 and equivalent grades ensures consistent quality and reliable performance.
Rapid Response & Flexible Lead Times
We fully understand the time-sensitive nature of power plant maintenance and turnaround schedules. Through optimized production workflows and a dedicated project management team, we are able to deliver prototype samples within 15–20 days and fulfill full production orders within 4–6 weeks (depending on quantity and complexity). Emergency rush orders are prioritized for expedited scheduling.
One-Stop Integrated Manufacturing Capability
Our facility is fully equipped with investment casting, EPC (expendable pattern casting), resin sand casting, and centrifugal casting production lines. Combined with our in-house CNC machining workshop, we deliver installation-ready finished air caps-complete with precision threading, flange machining, drilling, and surface finishing-eliminating the need for secondary processing by the customer.
Technical Support & After-Sales Service
We provide 24/7 technical consultation, covering material selection guidance, casting process optimization, installation support, and failure analysis assistance. Our engineering team is available to collaborate on custom alloy development and performance enhancement solutions tailored to specific operating conditions.
Contact & Inquiry
For customized boiler air cap quotations, technical datasheets, material certifications, or design consultation, please contact our sales engineering team with your drawings, quantity requirements, and operational parameters.We look forward to supporting your power plant operations with premium ZG40Cr25Ni20Si2 air caps that deliver extended service life and reduced maintenance downtime.
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