Common Gray Cast Iron Grate Bar Materials
The common grades for ordinary grey cast iron grate bars are HT200 and HT250. These materials cast well and cost little, but their heat resistance and thermal shock resistance are limited, so they suit small boilers at moderate temperature.
Temperature limit and properties
Grey cast iron bars have a maximum long-term service temperature of about 480-520℃, and above 600℃ they oxidise, grow and deform and crack very easily. Their strengths are excellent castability, lowest cost, easy machining, vibration damping and wear resistance, which suit simple thin bar structures; their weaknesses are poor heat resistance, poor thermal shock resistance, high brittleness, no resistance to sulphur corrosion, a sharp loss of strength at high temperature and short life.
| Item | Parameter |
|---|---|
| Common grades | HT200, HT250 |
| Maximum long-term service temperature | 480-520℃ |
| Over-temperature risk | Above 600℃, easy oxidation, growth, deformation and cracking |
| Typical service life | 3-6 months |
Where they are used
Grey cast iron bars serve small atmospheric coal-fired hot-water boilers, domestic heating boilers and fixed hand-fired grates; they suit low furnace temperature, small load swings and good anthracite or low-ash, low-sulphur coal. They are also chosen for budget-limited or short-term transitional projects, with a typical life of 3-6 months.
