Fig. 1. Key milestones in the development of boron steels and hot stamping technology^[20]

Fig. 2. Microstructure evolution and transient mechanical properties of steels during hot stamping^[8]

Fig. 3. Two kinds of hot stamping forming processes^[8]. (a) Direct hot stamping forming process; (b) indirect hot stamping forming process

Fig. 4. Mechanical properties of 22MnB5 steel in different states and other grades of steels^[30]

Fig. 5. Hot-formed parts of the Volvo XC90 body and their use ratio^[8]

Fig. 6. B-pillar with custom performance^[33]

Fig. 7. Weld section morphologies at different welding speeds^[51]. (a) 4 m/min; (b) 6 m/min; (c) 8 m/min; (d) 10 m/min

Fig. 8. Surface morphologies of weld seam with different defocusing distances^[52]. (a) 0 mm; (b) 3 mm; (c) 4 mm; (d) 5 mm; (e) 0 mm and 5 mm

Fig. 9. Weld section morphologies under different oscillation paths^[53]. (a) No oscillation; (b) vertical oscillation; (c) parallel oscillation; (d) circular oscillation

Fig. 10. Element distributions and microstructures of welded joints after hot stamping^[64]. (a) Metallographic diagram of the weld; (b) Al distribution; (c) Si distribution; (d)(e)(f) microstructures

Fig. 11. Microstructures of laser welded joint^[65]. (a)(b) With Al-Si coating; (c)(d) without Al-Si coating

Fig. 12. Load-depth (P-h) curves and corresponding indentation ^[66]. (a) Load-depth curves; (b) indentation before hot stamping;

Fig. 13. IPF diagrams of the microstructure of the welds with or without Al-Si coating^[67]. (a) (b) The boundary and center of the weld with coating; (c) (d) the boundary and center of the weld without coating

Fig. 14. Mechanical properties of welded joints after hot stamping^[67]. (a) Hardness distribution; (b) tensile properties

Fig. 15. Fracture location of cup process test^[72]. (a) Without Al-Si coating; (b) with Al-Si coating

Fig. 16. Microstructures and Al content of welds with different spot diameters^[78]. (a)(b) 0.22 mm; (c)(d) 0.54 mm

Fig. 17. Diagrams of dynamic behavior of welding pool with different laser^[81]. (a) Continuous wave laser; (b) pulse wave laser

Fig. 18. Micromorphologies of the coating^[83]. (a) Before arc pretreatment; (b) after arc pretreatment

Fig. 19. Microstructures of the weld^[84]. (a)(b) Without Ni foil; (c)(d) with Ni foil

Fig. 20. Schematic diagram of microstructure evolution^[85]

Fig. 21. Fe-Al phase diagrams calculated using JMatPro software^[86]. (a) Without Ni coating; (b) with Ni coating

Fig. 22. Fe-Al phase diagrams generated by JMatPro calculation of weld chemical composition^[87]. (a) Without graphite coating; (b) with graphite coating

Fig. 23. Relationship between ferrite content in weld and welding parameters^[88]