PRODUCTION OF WIRE ROD FOR COLD FORGING

摘要

PURPOSE:To produce wire rods of less decarbonized layers in steel surface and superior cold forgiability with a good productivity by annealing the hot-rolled wire rods made into quench structure in an inert gas while they are held stuck with scale. CONSTITUTION:The hot-rolled wire rods stuck with scale of 3-10mu thickness by cooling the same at >=4 deg.C/sec rate down to 600 deg.C to quench structure after hot rolling are subjected to spheroidizing annealing in an inert gas of <=0.05% moisture. Here, the cooling conditions are limited in order to form the quench structure and shorten the spheroidizing annealing time. The scale thickness below 3mu is insufficient in the effect of preventing the progression of decarbonization during annealing and that above 10mu increases the danger of peeling during handling up to annealing. The gaseous atmosphere for the spheroidizing annealing is limited because with a reducing gas the scale reacts to produce decarbonizable gases and with an oxidative gas, the decarbonization and oxidation progress simultaneously. The moisture in the inert gas is limited in order to prevent the considerable progression of decarbonization.