Plastic Gradient Coordination Behavior of Boron Steel/Q235 Steel Laser Welded Joint Under Welding with Synchronous Thermal Field

Guangtao Zhou; Huachen Li; Fang Liu; Hepeng Cui

doi:10.3788/CJL202148.0602109

Chinese Journal of Lasers, Volume. 48, Issue 6, 0602109(2021)

Plastic Gradient Coordination Behavior of Boron Steel/Q235 Steel Laser Welded Joint Under Welding with Synchronous Thermal Field

Guangtao Zhou^1,2、*, Huachen Li¹, Fang Liu¹, and Hepeng Cui¹

Author Affiliations

¹Fujian Key Laboratory of Special Energy Manufacturing, College of Mechanical Engineering and Automation, Huaqiao University, Xiamen, Fujian 361021, China

²State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China

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Figures & Tables(18)

Fig. 1. Principle of the welding with synchronous thermal field

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Fig. 2. Sampling position of the hot stretch specimen

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Fig. 3. Dimensions of the hot stretch specimen. (a) Integral joint; (b) each area of joint

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Fig. 4. Surface morphology of the boron steel /Q235 steel laser weld seam under the conventional condition

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Fig. 5. Yield strength distribution of the conventional welded joints at different temperatures

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Fig. 6. Surface morphology of the boron steel /Q235 steel laser weld seam under 450 ℃ thermal field condition

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Fig. 7. Experimental results of the joint as a whole under high temperature tension at 800 ℃. (a) Stress-strain curve; (b) elongation

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Fig. 8. Actual picture of the welded joint after being pulled off as a whole. (a) Conventional welding; (b) 300 ℃ thermal field; (c) 450 ℃ thermal field; (d) 600 ℃ thermal field

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$Micro morphology of the fracture. (a) Conventional welding; (b) 450 ℃ thermal field$

Fig. 9. Micro morphology of the fracture. (a) Conventional welding; (b) 450 ℃ thermal field

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Fig. 10. Stress-strain relationships of the each area of the welded joint. (a) Conventional condition; (b) 300 ℃ thermal field; (c) 450 ℃ thermal field; (d) 600 ℃ thermal field

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Fig. 11. Distribution of yield strength of welded joints at 800 ℃

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Fig. 12. Physical image of the specimens in each area of the welded joint after being pulled off at 800 ℃. (a) Weld; (b) HAZ of the Q235 steel; (c) HAZ of the boron steel; (d) base material of the Q235 steel; (e) base material of the boron steel

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Fig. 13. Microstructure of the boron steel/Q235 steel welded joints under different conditions. (a) Weld area under conventional condition; (b) boron steel HAZ under conventional condition; (c) Q235 steel HAZ under conventional condition; (d) weld area under 600 ℃ thermal field (e) boron steel HAZ under the 600 ℃ thermal field; (f) Q235 steel HAZ under 600 ℃ thermal field

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Table 1. Mass fraction of elements in materials unit: %
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Table 1. Mass fraction of elements in materials unit: %
Element C Mn Si Cr Mo B P S Fe
B1500HS 0.23 1.35 0.25 0.19 0.04 0.003 0.015 0.006 other
Q235 steel 0.18 0.54 0.26 -- -- -- ≤0.045 ≤0.05 other

Table 2. Dimensions of the hot stretch specimen unit: mm
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Table 2. Dimensions of the hot stretch specimen unit: mm
Symbol R L₀ L_c L d b₁ b₂
Value 25 24 70 110 31 2 12

Table 3. Optimum technological parameters of the boron steel /Q235 steel under conventional condition
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Table 3. Optimum technological parameters of the boron steel /Q235 steel under conventional condition
Welding condition Value
Average power /W 350
Peak power /kW 2.8
Welding speed /(mm·s^-1) 2
Heat input /(J·mm^-1) 140
Pulse width /ms 10
Laser frequency /Hz 10

Table 4. Optimum technological parameters of boron steel /Q235 steel laser welding under welding with synchronous thermal field condition
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Table 4. Optimum technological parameters of boron steel /Q235 steel laser welding under welding with synchronous thermal field condition
Temperature ofthermal field /℃ Averagepower /W Peakpower /kW Welding speed /(mm·s^-1) Heat input /(J·mm^-1) Pulse width /ms Laserfrequency /Hz
300 338 2.7 2.3 117 10 10
450 310 2.5 2.6 95 10 10
600 300 2.4 3.3 73 10 10

Table 5. Results of the high temperature tensile test of integral joints

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Table 5. Results of the high temperature tensile test of integral joints

Test temperature /℃	Welding condition	Tensile strength /MPa	Elongation /%
700	convention	179.514	15.83
	300 ℃ thermal field	142.871	17.50
	450 ℃ thermal field	127.283	18.43
	600 ℃ thermal field	114.984	19.09
Test temperature /℃	Welding condition	Tensile strength /MPa	Elongation /%
750	convention	122.342	25.04
	300 ℃ thermal field	97.332	27.50
	450 ℃ thermal field	85.964	28.95
	600 ℃ thermal field	78.437	29.02
800	convention	78.647	31.30
	300 ℃ thermal field	62.582	34.38
	450 ℃ thermal field	55.275	36.20
	600 ℃ thermal field	50.375	37.50
850	convention	52.933	33.41
	300 ℃ thermal field	42.135	36.70
	450 ℃ thermal field	37.465	38.60
	600 ℃ thermal field	33.914	40.03
900	convention	48.671	33.87
	300 ℃ thermal field	38.546	37.20
	450 ℃ thermal field	32.920	39.12
	600 ℃ thermal field	30.914	40.30
Room temperature	convention	475.498	7.20
	300 ℃ thermal field	410.896	8.01
	450 ℃ thermal field	350.432	8.84
	600 ℃ thermal field	311.501	10.21

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Guangtao Zhou, Huachen Li, Fang Liu, Hepeng Cui. Plastic Gradient Coordination Behavior of Boron Steel/Q235 Steel Laser Welded Joint Under Welding with Synchronous Thermal Field[J]. Chinese Journal of Lasers, 2021, 48(6): 0602109

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