Metallographic corrosion method for delta-ferrite in 2Cr13 martensitic stainless steel continuous casting billet

The invention discloses a metallographic corrosion method for delta ferrite in a 2Cr13 martensitic stainless steel continuous casting billet. The metallographic corrosion method comprises the following steps: sampling: sampling from the center of the continuous casting billet; grinding: sequentially grinding and flattening the sample by using abrasive paper; when each abrasive paper is replaced, rotating the sample by 30 degrees; polishing: putting the sample into a metallographic polishing machine, and polishing the sample until the surface is bright and free of scratches; cleaning and drying: adding water to wash the sample, wiping the sample with alcohol to remove residual polishing paste on the surface of the sample, and drying the sample; electrolyte preparation: pouring perchloric acid into a glacial acetic acid solution to prepare an electrolyte; electrolytic corrosion: pouring the obtained electrolyte into an electrolytic tank, connecting a cathode with the electrolytic tank, connecting an anode with