Dilution of electrode by base metal

[engr2GW]

Hi,
what does it mean for an electrode to be diluted by the base metal or (may be it's the other way round)
E.g. If E7010 and E8010 are used for the root pass of 70K and 80K tensile strenght materials, it is said that due to dilution with the base metal root bead cracking can occur, but using lower carbon equivalent E6010 helps mitigate root bead cracking without lowering the strenght of the weld joint.

Can someone please help me explain the dilution? it is a chemical phenomenon or does it just mean the base metal causing the weld metal to be lesser in strenght, and it it's the later, does that mean that in case of the E6010, it'll be the E6010 diluting the base metal/

Thank you.

 

[metengr]

Dilution in welding means mixing of elements from the weld rod with elements in the base material in the molten weld nugget region. You can calculate the percentage of elements from dilution, after solidification, based on the welding process used and a mass balance equation.

 

[metengr]

To follow-up with your second question as dilution occurs from welding, the resultant chemical composition of the solidified metal (within the weld region nearest the base material) can be more tolerant to cracking because of the effects of dilution. The effects of dilution can be lower strength but other problems can develop. One needs to weigh carefully the proper selection of filler metals.