Upsetting method of free forging press for ultrahigh-diameter-ratio large alloy steel ingot

The invention discloses an upsetting method of a free forging press for an ultrahigh-diameter-ratio large alloy steel ingot. The upsetting method comprises the following steps that the internal space of an upsetting cylinder is determined according to the size of a steel ingot before upsetting, and the proportional distribution of inner and outer steel ingot materials of the upsetting cylinder after upsetting is determined; the upsetting cylinder is placed on an upsetting platform, the heated steel ingot is placed in the upsetting cylinder, the steel ingot is extruded by a flat anvil, and upsetting in the cylinder is carried out; and the ingot blank subjected to intra-cylinder upsetting is taken out to be heated, the larger end of the ingot blank is placed on an upsetting platform 4 for extra-cylinder upsetting till a single-drum-shaped blank is formed, and upsetting of the steel ingot with a height-diameter ratio larger than 4.0 is completed. According to the method, the problems of instability, cracks and s