Microstructure and Toughness of Laser Welding Seam of Medium Manganese Automobile Steel

Yanjie Wang; Lin Zhao; Yun Peng; Yang Cao

doi:10.3788/CJL202249.0802021

Chinese Journal of Lasers, Volume. 49, Issue 8, 0802021(2022)

Microstructure and Toughness of Laser Welding Seam of Medium Manganese Automobile Steel

Yanjie Wang^1,2, Lin Zhao^1、*, Yun Peng^1、**, and Yang Cao¹

Author Affiliations

¹Institute of Welding, Central Iron and Steel Research Institute, Beijing 100081, China

²College of Materials Engineering, North China Institute of Aerospace Engineering, Langfang, Hebei 065000, China

show less

Abstract Get PDF(in Chinese)

Figures & Tables(17)

Fig. 1. Microstructure of medium manganese steel base material. (a) SEM image; (b) TEM image

Download full size

Fig. 2. Laser welding platform for medium manganese steel

Download full size

Fig. 3. Cross-sectional morphologies of welded joint under different heat inputs. (a) 150 J/mm; (b) 300 J/mm；(c) 375 J/mm; (d) 500 J/mm

Download full size

Fig. 4. SEM images of weld zone under different heat inputs. (a) 150 J/ mm; (b) 300 J/ mm; (c) 375 J/ mm；(d) 500 J/mm

Download full size

Fig. 5. TEM images of manganese steel weld zone under different heat inputs. (a) 150 J/mm; (b) 150 J/mm；(c) 300 J/mm; (d) 500 J/mm; (e) EDS of precipitated phase

Download full size

Fig. 6. Hardnesses of welded joints under different heat inputs

Download full size

Fig. 7. Impact energies of welds at－40 ℃ under different welding heat inputs

Download full size

Fig. 8. Impact energies and oscillographic impact curves of welds under different heat inputs. (a) 150 J/mm；(b) 300 J/mm; (c) 375 J/mm; (d) 500 J/mm

Download full size

$Impact fracture morphologies of welds under different heat inputs. (a) 150 J/mm; (b) 300 J/mm; (c) 375 J/mm；(d) 500 J/mm$

Fig. 9. Impact fracture morphologies of welds under different heat inputs. (a) 150 J/mm; (b) 300 J/mm; (c) 375 J/mm；(d) 500 J/mm

Download full size

Fig. 10. Orientation maps of microstructures in weld zone under different heat inputs. (a) 150 J/mm; (b) 300 J/mm；(c) 375 J/mm; (d) 500 J/mm

Download full size

$Microstructural morphology, orientation, and grain boundary distribution in crack propagation zone of impact fracture when heat input is 150 J/mm. (a) Fracture sectional structure; (b) reverse pole diagram of fracture section; (c) angular distribution of fracture section$

Fig. 11. Microstructural morphology, orientation, and grain boundary distribution in crack propagation zone of impact fracture when heat input is 150 J/mm. (a) Fracture sectional structure; (b) reverse pole diagram of fracture section; (c) angular distribution of fracture section

Download full size

Table 1. Chemical compositions of medium manganese steel
View table
Table 1. Chemical compositions of medium manganese steel
Element C Si Mn Al S P Fe
Mass fraction /% 0.1200 0.0820 4.8300 0.0330 0.0091 0.0008 Bal.

Table 2. Laser welding process of medium manganese steel
View table
Table 2. Laser welding process of medium manganese steel
Experimental group Power /kW Welding speed /( m·min^－1) Heat input /( J·mm^－1) Defocusing /mm
Group 1 5 2 150 0
Group 2 5 1 300 0
Group 3 5 0.8 375 0
Group 4 5 0.6 500 0

Table 3. Cross-sectional sizes of weld seams under different heat inputs
View table
Table 3. Cross-sectional sizes of weld seams under different heat inputs
Size 150 J/mm 300 J/mm 375 J/mm 500 J/mm
Upper surface melting width 1.84 2.50 3.18 6.06
Upper neck width 0.78 1.18 1.27 2.23
Bottom surface width 0.79 2.03 2.92 3.14

Table 4. Oscillographic impact results of welds

View table

Table 4. Oscillographic impact results of welds

Heat input /(J·mm^－1)	E₁ /J	E₂ /J	E₁+E₂ /J	E₃ /J	E₄ /J	E₃+E₄ /J	E₅ /J	E_total /J	F_gy /kN	F_m /kN	F_im /kN	F_a /kN
150	1.74	11.58	13.32	3.40	5.33	8.73	3.93	25.98	6.49	8.94	6.10	1.43
300	6.65	29.72	36.37	7.25	6.20	13.45	2.04	51.86	10.60	13.80	12.35	2.60
375	6.41	26.86	33.27	3.32	2.00	5.32	1.83	40.42	11.10	14.26	12.25	1.08
500	1.14	5.90	7.04	1.38	0.47	1.85	0.09	8.98	7.28	11.65	9.47	3.14

Table 5. Weld grain sizes and crack propagation energies under different heat inputs

View table

Table 5. Weld grain sizes and crack propagation energies under different heat inputs

Heat input /(J·mm^－1)	Width of austenite columnar crystal /μm	Average effective high angle grain size /μm	Crack propagation energy at－40 ℃ /J
150	12.8	1.972	8.73
300	15.4	1.775	13.45
375	18.8	2.289	5.32
500	26.3	2.464	1.85

Table 6. Proportions and densities of high-angle grain boundaries of welds under different welding heat inputs

View table

Table 6. Proportions and densities of high-angle grain boundaries of welds under different welding heat inputs

Heat input /(J·mm^－1)	Proportion of high-angle grain boundary /%	Length of high-angle grain boundary /μm	High-angle grain boundary density /(mm·mm^－2)
150	22.44	23797	793
300	25.22	26751	892
375	16.96	17981	599
500	15.26	16185	539

Tools

Get Citation

Copy Citation Text

Yanjie Wang, Lin Zhao, Yun Peng, Yang Cao. Microstructure and Toughness of Laser Welding Seam of Medium Manganese Automobile Steel[J]. Chinese Journal of Lasers, 2022, 49(8): 0802021

Download Citation

EndNote(RIS)BibTex Plain Text

Set citation alerts for article

Save article for my favorites