1. Influence of the surface defects concerning drawing processes of the micro-alloyed steel Stanislav Rusz

2. Introduction Effect of the pass reduction concerning the strain course in wires made of micro-alloyed steel, 23MnB4; namely successively investigating three particular points before the die, before the die, in the die itself, in the die itself, at the die output section at the die output section

3. Experiments Four variants of wire drawing reduction have been analysed: Reduction, Ø 14 – Ø 12.1 mm; Friction coefficient, 0.1 Reduction, Ø 14 – Ø 12.1 mm; Friction coefficient, 0.1 Reduction, Ø 14 – Ø 12.1 mm; Friction coefficient, 0.15 Reduction, Ø 14 – Ø 12.1 mm; Friction coefficient, 0.15 Reduction, Ø 14 – Ø 11.8 mm; Friction coefficient, 0.1 Reduction, Ø 14 – Ø 11.8 mm; Friction coefficient, 0.1 Reduction, Ø 12.1– Ø 11.8 mm; Friction coefficient, 0.1 Reduction, Ø 12.1– Ø 11.8 mm; Friction coefficient, 0.1

4. Simulation process Fig.1: Network – Initial condition, (a), Network by final drawing process (b) a)b)

5. Temperatures simulation Fig.2: Material deformation curves produced by upsetting tests for temperatures of 20 and 200 °C

6. Drawing force Fig.3: Course of drawing force – Var. a

7. Surface strain Fig.4: Surface strain at the cross-section locale, R-R – Var. a Gauge of drawing dieUnloading

8. Strain condition analysis (example for reduction, Ø 14 – Ø 12.1 mm) Fig.5: Axial strain by drawing and after release [MPa] – Var. a

9. Plastic transformation Fig.6: Plastic transformation – Overview, Var. a

10. Results Significant residual pressure strains are retained along the axis - especially as axial oriented Significant residual pressure strains are retained along the axis - especially as axial oriented On the contrary the surface retains such values that are undesirable as regards the risks of its damage On the contrary the surface retains such values that are undesirable as regards the risks of its damage The plastic deformation, a very intensive deformation takes place at the wire surface after the passage through the die, as well as in the specimen’s centre. The plastic deformation, a very intensive deformation takes place at the wire surface after the passage through the die, as well as in the specimen’s centre. The intensive deformation works on behaviour of surface defects. The intensive deformation works on behaviour of surface defects.

11. Axial Strains Fig.7: Axial strain course in various points of the die

12. The process analyse of the wire drawing with lengthwise defect Fig.8: Network initial shape for the defect neighbourhood Fig.9: Defect’s closing by passing through the die – Detail

13. Perimeter movement and deformation intensity Fig.10: Perimeter movements by drawing [mm] Fig.11: Deformation intensity on the defect’s level - Detail

14. General assessment The results provide evidence for the fact that an action of upsetting a cylindrically shaped specimen with lengthwise defect results in a gaping effect. The results provide evidence for the fact that an action of upsetting a cylindrically shaped specimen with lengthwise defect results in a gaping effect. This is an unfavourable condition. On the contrary, an action of drawing a sample with the same defect leads explicitly to its closing, which is evident in the detail of the Fig. 8 and 9. This is an unfavourable condition. On the contrary, an action of drawing a sample with the same defect leads explicitly to its closing, which is evident in the detail of the Fig. 8 and 9.

15. The value for this closing after drawing illustrates Fig. 10, where the blue colour indicates in millimetres the peripheral movement of defect edges in the direction of its closing; contrary to this, red indicates opening. The value for this closing after drawing illustrates Fig. 10, where the blue colour indicates in millimetres the peripheral movement of defect edges in the direction of its closing; contrary to this, red indicates opening. The movement value, –0.04 mm, for each edge towards the centre means that the defect does not close completely, but its width decreases from 0.1 to 0.02 mm The movement value, –0.04 mm, for each edge towards the centre means that the defect does not close completely, but its width decreases from 0.1 to 0.02 mm

16. The material remains permanently transformed to the effect of defect closing. The material remains permanently transformed to the effect of defect closing. The maximum deformation, 0.37, the same situation implies the value, 0.42, for a smooth defect-free surface. The maximum deformation, 0.37, the same situation implies the value, 0.42, for a smooth defect-free surface. Further investigations will have to concentrate on experimental verifications of strain condition influence concerning closing of surface defects by producing high-strength bolts. Further investigations will have to concentrate on experimental verifications of strain condition influence concerning closing of surface defects by producing high-strength bolts.

17. Thank you for your attention Thank you for your attention