Test materials and methods of gray cast iron under low frequency thermal fatigue load

1. High temperature oxidation cycle test

The size shall be 30 mm in a muffle furnace × 30 mm × 220 mm HT200 gray cast iron test block shall be heat treated, and the maximum heat treatment cycle is 50. The air atmosphere is maintained in the furnace to form a high-temperature oxidation environment. The specific heat treatment system is shown in Figure 1.

2. Hot tensile test of gray cast iron

The gray cast iron test block after high temperature oxidation treatment is processed into Φ 10 mm × For 100 mm tensile sample, Gleeble-1500 thermal simulation testing machine shall be used to test the high-temperature tensile strength of the sample. The specific tensile system is shown in Figure 2.

3. Tensile analysis method of gray cast iron

The fracture surface of gray cast iron tensile sample was ground and polished. The graphite morphology and matrix phase composition near the fracture surface before and after erosion were observed by neophot21 optical microscope. The erosion agent was 4% nitric acid alcohol. The fracture morphology of the tensile specimen was observed by jsm-6480lv scanning electron microscope, and the element composition of the phase near the fracture was analyzed by NORAN osix energy spectrometer.

The morphology of graphite and matrix of gray cast iron samples at different times was observed by vl2000dx-svf17sp ultra-high temperature laser confocal microscope. Under vacuum, the gray cast iron sample is heated at 10 ℃ · min-1 from room temperature, kept at 900 ℃ for 10 min, and then reduced to room temperature at 10 ℃ · min-1.

The gray cast iron samples after high temperature oxidation treatment are sent to the national iron and steel materials testing center to test the contents of carbon and silicon. The testing standards are GB / t20123-2006 and GB / T 223.60-1997 respectively.