Fig. 1. YOLOv7Tiny frame diagram

Fig. 2. Structure of each module in YOLOv7Tiny. (a) Structure diagram of CBL module; (b) structure diagram of ELAN module;

Fig. 3. Structure diagram of improved YOLOv7Tiny

Fig. 4. Structure diagram of S-ELAN module

Fig. 5. Data annotation process

Fig. 6. Defect images after data augmentation. (a) Original defect image; (b) after horizontal rotation; (c) after vertical flipping; (d) after randomly adjusting image brightness; (e) after adding salt and pepper noise; (f) after adding Gaussian noise

Fig. 7. Mosaic data augmentation

Fig. 8. Comparison of models detection effects

Fig. 9. Comparison of detection effect for slag inclusion defects in small target types. (a) Detection effect of the original model; (b) detection effect of the improved model

Fig. 10. Comparison of detection effect for three types of defects. (a) Detection effect of the original model; (b) detection effect of the improved model