Butt welding hardenable steel chains via hydraulic pressure - where non-return valve in hydraulic circuit prevents loss of pressure when switching from welding to upsetting pressure

摘要

The steel contain >0.15% C, and >0.5% Cr; and can be hardened and tempered to mfr. high tensile chains. To avoid a drop in hydraulic pressure when switching over from the welding pressure (Pw) to the upsetting pressure (Pu), a non-return valve (Vnr) is connected in parallel with the pressure switch over valve (Vso) in the hydraulic control circuit of the welding machine. Valve (Vnr) is fed with the oil used to apply Pw, and therefore keeps the work cylinder at Pw during switch-over to the welding pressure. The time at which switch-over occurs can pref. be freely selected in the electronic control circuit on the machine. The invention can pref. also be used on flash butt welding machines. During heating for welding, no spray occurs and the joint surfaces are protected against oxidn. so strong welds are obtd.