Boron steel - welding

[lukkaa]

Hello,
I would like to ask you for your opinion.

I have a high strength low alloy chain steel (0,2-0,25% C, 1% Ni, 0,5% Mo, 0,5%Cr) with addition of boron (0,002-0,0035%). For the suppression of boron nitride precipitation is this steel sufficiently titan treated (nitrogen about 0,006%).

So, there is a problem with welding this steel together. It is used a flash-butt welding and this steel is tested after a heat treatment (quenching and annealing). And after a heat treatment a majority of welded chain links disrupted at weld joint. The fracture is clear brittle.

What do you think, could be this problem caused by presence of boron (in spite of titan treating)?

Thank you for any answer

 

[owenmaterials]

Lukkaa,

The following link may give you a clue:

 

[dbooker630]

You may want to check a micro in the as-welded condition and note the hardness and microstructure of the heat affected zone. That might indicate the propensity for fracture even before heat treatment.

 

[TVP]

I don't think the problem is due to boron nitride formation. Definitely check microstructure in the weld and heat affected zone before heat treating.

 

[metengr]

Agree with dbooker630 and yes, most certainly, boron will adversely effect weld joint properties.

 

[stanislasdz]

Here a link for a very good paper :

Effect of residual boron on the microstructure of low-carbon steel resistance-seam welds

http://mc-mjnde.ornl.gov/PNGV/publications/Boron_WJ/Boron.html

Hope this will help