Abstract: The first all-welded 12,000-ton hydraulic forging press was built by electroslag welding in China. The work bagnn in February 1959 and was completed at tile end of 1961.13y dune 1002, the press, being complotly assembled, was put into service. It had been successfully designed and manufactured under the guidance of tile principles of relying oil our own efforts find ninking full use of local production conditions at that time.The press call be used to forge alloy stool Ingots of about 100 tons and, if necessary, carbon stool ingots as hoavy us 250 tons or so. The use of the press can facilitate the manufacture of the large forgings required for building metallurgical,. Chemical and power station equipments as wall as many other industrial equipments, It is one of the most important oquipments indispensable to the development of national antisfnetory.The reason 1 why the hydraulic press Is said to ho all-welded is that roll-welded and cast-welded structures of carbon steel and low alloy steel aroused ill tile manufacture of the largo components of tlio press. The throe largo crosabonms(crown, slide and bed-plate) fire ofpluta-steolwelded Instond of tile usual east steel structures, and the tie rods and the actuating cylinders are of cast stool woldod instead of the usual all-forged structures. That Is why welding bacolnas all Important oporatlon In manufacturing the. Press. Tho nniount of welding ill trio whole manufacturing process Is so great that it is rarely found in llio World with presses of siuiilar capacity. Owing to the success fn utilizing Clio efficient olectroslng welding-ono of the achievements In inodornwolding tech niqurs, ilia problem of welding such largo structures has ,loon solved successfully, and tile quality of the press is found satisfactory. The success In building such n hydraulic press ,lot only allows trio technical and eco oinical significance of wolding In manufacturing licnvy duty machines with parts of great thicknesses, but also sets n brilliant oxnlliplo to, those localities or districts Ill want of great casting and forgIng oqulpments (generally of more than 100 ton casting capacity and 10,000 toll forging capacity). Those areas may also be able to set up. And . Develop in a short period of time the heavy duty machine-building industry under, ilia guidance of time prnciples of relying oil Chair own efforts and ranking full use of the existing equipments and production potentialities. The components of the hydraulic press are too many to be described exhaustively here in this paper, therefre our attention call only be directed to tile descriptions of the manufacture of the crossbeams and the tie rods-the two main parts of the press-by welding, and especially of the elactroslng welding technology; as to other problems, only a brief illustration Is given.