Effect of Process Parameters on Mechanical Properties of DP780 and BH210 Single-Side Resistance Welds

Transcription

1 Effect of Process Parameters on Mechanical Properties of DP780 and BH210 Single-Side Resistance Welds Ramakrishna (Rama) Koganti, Sergio Angotti, Arnon Wexler, Shawn Morgans Ford Motor Company Yan (Jack) Sang, Patrick Morin, Chonghua (Cindy) Jiang AET Integration, Inc Wim Lam, Karel Pieterman Arplas Welding System Christopher Karas Metro Technologies Ltd.

2 Scope of Work Develop single-side resistance welding process parameters for electro-galvanized DP780 and hot-dip galvanized BH210 steels Metallurgical properties of the welds Weld profile Microhardness Traverse Mechanical properties of the welds Tensile properties Shear tension Cross-tension Fatigue life Shear tension

3 Materials 1.0 mm electro-galvanized DP mm hot-dip galvanized BH210

4 Joint Design: Shear Tension Dimple orientation (single-side) Dimple orientation (single-side) Dimple orientation (single-side) (double-side)

5 Joint Design: Cross-Tension 150 mm 150 mm 50 mm 50 mm 50 mm 50 mm Single-side Double-side

6 Experimental: Welding Arplas single-side resistance welding system Pedestal Dimpler Single-Side Welder

7 Welding Parameters Studied: Single Side Welding Dimple orientation % of Power Electrode force

8 Experimental: Metallurgical Examination Single-side: Cross-sections were cut at mid point of the weld and perpendicular to the dimple orientation Double side: Cross-sections were cut parallel to the line of tensile force

9 Experimental: Microhardness Traverse Load: 500g Distance between two adjacent indentations: 0.4 mm

10 Experimental: Mechanical Testing Tensile testing: AWS D8.9 Fatigue testing: Referencing ASTM E466 Constant amplitude sinusoidal load history R=0.1

11 Weld Profile and Microhardness Traverse: BH210 Single Side Weld Double Side Weld No.9 Bottom sheet Top sheet No degree, 600N, 50% No No.11 Microhardness (HV500g) Microhardness (HV 500g) Distance (mm) Distance (mm)

12 Weld Profile and Microhardness Traverse: DP780 No.8 No.4 Single Side Weld Double Side Weld No No Hardness (Vikers 500g) Hardness (Vikers 500g) Distance (mm) Distance (mm) No HAZ softening was observed for the single-side weld

13 Effect of Welding Parameters on Tensile Strength (Shear Tension): BH Tensile Strength (N) A1,Horizontal 600N 40% A2,Vertical 600N 40% A3,45 degree 600N 40% B1,Horizontal 600N 50% B2,Vertical 600N 50% B3,45 degree 600N 50% C1,Horizontal 1000N 50% C2,Vertical 1000N 50% C3,45 degree 1000N 50% D1,Horizontal 1000N 60% D2,Vertical 1000N 60% D3,45 degree 1000N 60% E, Conventional Spot Weld 0 Welding Condition It appears that tensile strength increases as power increases in this study. Dimple orientation does not appear to have significant impact on tensile strength. Tensile strength of single-side resistance welds is about 88% of that of conventional spot welds with 4.0 mm button size.

14 ANOVA: Factors affecting Tensile Strength (Shear Tension)-BH210 - Weld Force, and Power are significant Factors - Interaction between Dimple Orientation and Weld Force is also significant

15 Main Effect Plot-BH210 Main Effects Plot for Tensile (N) Data Means Dimple Orientation Force (N) Mean degree Horizontal Power (%) Vertical high low high low It shows that Power and Force have significant impacts on shear tension strength of single-side resistance welds.

16 Interaction Plot: BH210 Interaction P lot for Tensile (N ) Data M eans D im p le O r ie n ta tio n high lo w high lo w Dimple Orientation 45 d eg ree Horizontal Vertical Force (N) Force (N ) high lo w P o w e r ( % ) Power and Force interaction has significant effects on shear tension strength.

17 Effect of Welding Parameters on Tensile Strength (Shear Tension): DP Load (N) %power 1000N 45 Degree 40%power 1000N Vertical 40%power 1000N Horizontal 40%power 800N 45 Degree 40%power 1200N 45 Degree 40%power 800N Vertical 40%power 800N Horizontal 50%power 1000N Horizontal 50%power 1000N 45 Degree 50%power 1200N 45 Degree 50%power 1000N Vertical 50%power 800N 45 Degree 50%power 1400N 45 Degree 50%power 800N Vertical 50%power 800N Horizontal conventional spot weld 60%power 1000N 45 Degree 0 Weld Condition The shear tension strength of single-side welds is about 70% of the conventional spot welds for 1.0mm DP780 steels.

18 Cross Tension Strength: BH Load (N) % Power 1000N force 60% Power 1000N force 60% Power 1200N force Welding condition conventional spot weld Test results indicates that cross tension strength of single-side welds is about 70% of that of the conventional spot weld joints for 0.8mm BH210.

19 Cross Tension Strength: DP Load (N) % power 1400N force 60% Power 1200N force 60% power 1400N force 60% power 1600N force Welding Condition 70% power 1600N force conventional spot weld Test results indicates that single-side welds of 1.0mm DP780 have roughly the same cross tension strength as that of conventional spot welds.

20 Fatigue Life: BH210 Max. Load (lbs) R=0.1 Base Metal: 0.8 mm BH210 GI 50% 1000N diagonal 50% 600N diagonal 50% 1000N Longitudinal 50% 600N Longitudinal 50% 1000N Transverse 50% 600N Transverse Conventional Spot Welds Cycles to Failure It appears that welds with longitudinal dimples have better fatigue performance than welds with transverse dimples.

21 Summary Dimple orientation appears to have no significant effect on the tensile strength of single-side resistance welds in this study. High power and high force combination (no significant expulsion) yields higher tensile strength. Tensile strength of single side welds is about 70% (in the case of 1.0mm DP780) to about 90% (in the case of 0.8mm BH210) of the conventional spot welds. Cross tension strength of single side spot welds is about 70% (in the case of 0.8mm BH210) to 100% (in the case of 1.0mm DP780) of the conventional spot welds. Dimple orientation appears to affect fatigue performance of the single-side BH210 welds. Welds with longitudinal dimples seems to have better fatigue performance than welds with transverse dimples.

22 Summary (continued) Due to the low heat input of the process, the heat-affected zone of the single-side resistance welds is significantly smaller than those of the conventional resistance spot welds for both 0.8mm BH210 and 1.0mm DP780. No clear demarcation between base metal and weld metal was observed for the single side resistance weld of BH210. No HAZ softening of DP780 single-side welds was observed.