The development of cast iron technology at home and abroad requires that gray iron castings not only have good mechanical properties, but also perform well in the evaluation of eutectic (SC), maturity (RG), relative strength (RZ), hardness (Hg), relative hardness (RH) and quality coefficient (QI), In order to achieve the perfect combination of casting properties, mechanical properties and processing properties of gray iron parts and meet the needs of actual production. The table shows the quality evaluation results of gray iron castings with different contents of scrap steel (1-3 samples).

Since the set composition is the same, it can be seen from the calculation formula that the SC (an index to measure the graphitization degree of cast iron) of the three are not much different; However, in terms of RG (indicating the relationship between eutectic degree and tensile strength), Hg (indicating the relationship between eutectic degree and actual measured hardness), RZ (indicating the relationship between hardness and tensile strength) and Rh (indicating the relationship between strength and hardness), the value of sample 3 is closer to 1, and the deviation of the value is smaller than that of sample 1-2, This indicates that the molten iron of sample 3 has high metallurgical quality stability. In addition, Qi (comprehensive index) of sample 3 is also the largest. Therefore, No. 3 sample is better in terms of metallurgical quality, casting performance, mechanical properties and processability, and has excellent comprehensive properties.

In the table: