What is the significance of cast iron grades?
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What do the various letters in gray cast iron HT200 and ductile cast iron QT350-22R QT350-22L stand for?
HT200 indicates a minimum tensile strength of 200 MPa, and is suitable for components subjected to high loads
QT stands for ductile cast iron, 350 represents the tensile strength, 22 represents the elongation rate. R indicates that the material of this grade requires impact resistance at low temperatures (–20°C or –40°C); it also means that this grade of material needs to have impact resistance at room temperature (23°C). HT stands for gray cast iron
I made a mistake; the first R should be changed to “L””