Common Heat-Resistant Cast Iron Materials for Grate Bars

Heat-resistant cast iron is the mainstream mid-range material and the most common grate material for industrial chain grates. Under GB/T 9437 it falls into 3 series: silicon, chromium and aluminium.

1. Medium-silicon heat-resistant iron RTSi5 (RQTSi5)

Service temperature 750-900℃. Silicon improves oxidation resistance and resistance to high-temperature growth, and the iron casts well at moderate cost; the drawback is fairly high brittleness, so rapid heating and cooling crack it. It suits small and medium coal-fired chain grates, reciprocating grates and atmospheric biomass boilers at moderate temperature.

2. Chromium heat-resistant iron RTCr2, RTCr16

RTCr2 serves to 800℃ and is the general basic heat-resistant iron; RTCr16 is a high-chromium iron serving to 950℃ with much better oxidation and sulphur corrosion resistance. Chromium irons are tougher than silicon iron and resist sulphide corrosion in flue gas better, but cost more. They suit industrial steam coal boilers, high-sulphur coal firing and medium-load chain grates, and are the most widespread material in Chinese industrial boilers.

3. High-aluminium iron and its limits

High-aluminium heat-resistant iron serves to 1000℃ at moderate cost, but is the most brittle and poorest in thermal shock, so it is used only on fixed grates at stable temperature without frequent starts and is being replaced. Overall, heat-resistant cast iron is the value choice for small and medium industrial coal and biomass boilers, and is unsuitable for waste incineration, very hot furnaces, boilers with frequent starts and high-chloride corrosive flue gas.