Forging is the key stage of rail flash welding. K-series welding machine has the characteristics of narrow heating width and steep heating temperature field. However,compared with GAAS80 type fixed welding machine,the performance parameters of upsetting such as upsetting force and speed are deficient. The upsetting control program of K-1000 type fixed welding machine and the structure of upsetting oil circuit are reformed. The purpose of improving the speed of upsetting and keeping pressure is to improve the function of electrified forging stage. The results show that the adjustment and optimization of the hardware can satisfy the adjustment range of the upsetting process parameters and improve the quality of the rail welding head,especially for Quenched and corrosion resistant rail high alloy steel grades.