Metallographic structure and mechanical properties of ductile iron castings for low pressure inner cylinder of thermal power plant

According to the technical requirements, the metallographic inspection shall be carried out for the spheroidal ductile cast iron blank, and the attached test block shall be taken. The inspection results are shown in Figure 1 and Table.

Inspection itemsSpheroidization gradeGraphite sizeFerritePearliteCementiteOrganization
Standard valueLevel 1-3Grade 5~7≥ 95%≤ 5%≤ 1%Ferrite+graphite
Measured valueLevel 2Grade 6> 95%< 5%0Ferrite+graphite

According to the technical requirements, the NDT test was carried out on the nodular cast iron blank, and the test results met the requirements, as shown in Figure 2.

Inspection itemsYield strength/MPaTensile strength/MPaElongation after fracture (%)Brinell hardness (HBW)Room temperature impact absorbed energy/J
Standard value≥ 240≥ 370≥ 12130~180Average value ≥ 12, single value ≥ 9
Measured value26739225.513818,19,19
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