Projection Welding with HSLA Steel

[robo90124]

I am working on an automotive application involving welding a 7/16" projection weld nut to 1.8mm High Strength Low Alloy Steel. (SP253-590) I am having a difficult time developing optimum weld parameters to maintain the specified push out requirement. Has anyone done a study on projection welding with HSLA steel or have any suggestions?

 

[TVP]

What type of projection weld nut are you using? Hex with 3 projections? Other? The best standard that I have seen on this subject is DaimlerChrysler Process Standard PS-1804 WELD NUTS - PROJECTION WELDING. For the above mentioned weld nut, the following parameters apply:

Electrode force = 8900 N (2000 lbs)
Weld time = 16-20 cycles
Current = 23-25 K-amps

The required push-off force should be 18680 N (4200 lbs) and the Torque to failure should be 271 Nm (2400 in-lbs). Other parameters are given for different combinations of weld nut geometry and sheet metal thickness. You can obtain this standard from AutoWeb using the following link:

http://afx.autoweb.net/standards/

 

[robo90124]

The 7/16" nut is square with (4) projections. The projection height is 1.3mm

Does the DC PS-1804 cover different metals Low Carbon, Galanized, Galvanealed, HSLA.....????

 

[CoryPad]

robo90124,

I recommend that you stop using the 4-projection square nut and replace it with a suitable 3-projection nut. With 4-projection nuts, often one projection is significantly out of plane. The variable weld cross-section causes welding problems which in turn causes low mechanical properties. An analogy is a table with 4 legs - three legs define a plane with the floor, and one of the legs is out of plane and requires a sugar packet to prevent table movement.

 

[TVP]

The DC standard acknowledges that different substrates (HSLA, galvanized, etc.) are used, but does not necessarily have different performance requirements or weld parameters.

 

[dkelly]

Hi Robo
Is your material a "coated material" ie galvaneal, galvanized, hot dip ? as the thickness of coating can have a significant effect on weld integrity.