Chain grate stoker material

Chain grate stokers are commonly used combustion equipment in industrial boilers. Their materials must meet the requirements of high-temperature resistance, wear resistance, oxidation resistance, and a certain mechanical strength. The material selection for different components varies, as detailed below:

I. Core Load-Bearing Components: Beams
The beams are the main load-bearing structure of the stoker, supporting the grate bars, fuel, and mechanical loads generated by combustion, while also withstanding temperatures of 300-600℃ inside the furnace (depending on the boiler type).

● Common materials: Ordinary carbon structural steel (such as Q235) or low-alloy structural steel (such as Q345).
Q235: Low cost, moderate strength, suitable for low and medium temperature conditions (≤400℃) in small boilers.
Q345: Higher strength, better toughness, slightly better temperature resistance than Q235, suitable for boilers with larger loads or slightly higher temperatures.
● Characteristics: These steels have good weldability and can be formed by casting or welding to meet the structural stability requirements of the beams.

II. Components in Direct Contact with Flames: Grate Bars
Grate bars are in direct contact with the fuel (coal, biomass, etc.) and are in a long-term high-temperature (600-1000℃), mechanical friction (fuel movement), and oxidation corrosion environment, requiring the highest material requirements.

● Common materials:
Heat-resistant cast iron:
Such as HT250 heat-resistant cast iron (a type of gray cast iron, with added chromium, nickel, and other alloying elements), RQTSi5 heat-resistant ductile iron (ductile iron, containing silicon, rare earth, and other elements).
Characteristics: Good heat resistance (can withstand 600-800℃), excellent casting performance, moderate cost, suitable for small and medium-sized boilers.
● Heat-resistant steel:
Such as Cr25Ni20 (310S), 1Cr18Ni9Ti (321), etc., austenitic heat-resistant steels.
Characteristics: High temperature resistance (can withstand 800-1100℃), strong oxidation resistance and creep resistance, suitable for large boilers or high combustion temperature conditions (such as using high calorific value fuels), but higher cost.

III. Other Auxiliary Components:
1. Chains and sprockets:
Chains are responsible for driving the grate bars, and sprockets transmit power. They need to be wear-resistant and tensile-resistant.
Material: Usually No. 45 steel (medium carbon steel, with tempering treatment to improve strength and wear resistance), or alloy structural steel (such as 40Cr, to enhance hardness and toughness).
2. Grate pins (connecting shafts):
Connect the grate bars and chains, requiring shear resistance and wear resistance.
Material: Mostly No. 45 steel or 20Cr (after carburizing treatment, the surface is hardened to improve wear resistance).

Summary:
The material selection of chain grate stokers needs to consider working temperature, mechanical load, and cost comprehensively:

● Low temperature, light load conditions: mainly heat-resistant cast iron (grate bars) + Q235 steel (beams, chains);
● High temperature, heavy load conditions: grate bars use heat-resistant steel (such as 310S), beams and chains use low-alloy steel to ensure equipment life and operational stability.