Just come back from Halfords and on the door was a notice recalling a type of tow ball they sell. Seemingly the weld can crack an shear causing what ever is being towed to drop, could be nasty. Have had a look on their web site and found nothing. Sorry did not have enough time to photo or take down all they details.
Do you mean the welds have cracked on the TOWBAR?
Towballs are heated to a very high temperature and drop forged in a die (mould) from one piece of metal in order to bend rather than snap. No welding process is incorporated in the manufacturing process of the towball.
You are right not a weld, was in a rush. It is the bolt on type of tow ball and the picture shows between the bold hole and the ball neck (if that makes sense).
The towball and flange are usually forged in one piece as well making sure that there is no break in the material grain. The only parts that are machined afterwards (on an Al-ko towball) is the recess under the ball itself to allow the swivel of the stabiliser and the rear flat part of the flange (behind the 2 x 16mm. bolt holes) which is milled to make it flat where it meets the the towbar flange. However, if the crack is evident in the towball itself then it must be porrosity (air pockets) but that only usullally occurs when a component is cast and not forged which I would suggest that although it maybe a cheaper alternative to manufacture it won't be fit for purpose which is probably the case here.
Strangely, there is a European standard to comply to for all towbar manufacturers but cannot find the corresponding standard to meet for forged towballs.