【正文】
eveloped line frequency coreless bathroom plug stem bottom note type electric insulation casting. In 1982, hospital and Beijing the casting machine research cupola tuyere oxygen blowing technology. 19851988, Beijing institute of machine of floating end face seal ring by die successful test pressure casting process. In 1959, Beijing second metalforming machinery general factory changed (Beijing) built 2500 ton heavyduty hydraulic press. In 1971, the factory produced 6,000 tons, which is then Beijing hydrtesting biggest metalforming equipment. 19681979, Beijing hoisting machine factory has 300 tons of using hydraulic press 2000 tons and create crane and large panel. In the 1980s, Beijing institute of electrical and developed a series of Beijing mould centre highprecision cutting die, the multistage close to or to import mould level, changed Beijing precision punching moulds dependence on imports. Before 1949, Beijing has heat treatment furnace, salt dissolved by thermocouples means furnace, quenching and tempering, parts of annealing, normalizing, quenching and tempering, carburizing and etc. In 1956, Beijing first began using highfrequency quenching machine tool plant. In 1961, the Beijing second machine tool plant began using gas nitriding quenching. In 1969, the following enterprise by Beijing gage start light quenching. In 1978, the plete machine tool research institute of Beijing guide surface contact quenching process and equipment, quenching condition of quality inspection. In 1979, scientific research institute of China academy of railway and mechanical institute of highpower diesel engine cylinder collaboration of surface modification of laser. In 1979, Beijing institute of electrical carbon dioxide laser is developed, and the kilowatt in early 1980s respectively applied in cylinder and stamp printing equipments of laser treatment. Among them, tsinghua university, Beijing, Beijing institute of electrical YouPiaoChang jointly pleted YouPiaoChang seven color machine DaKongQi laser surface strengthening research. From 1984 to 1990, Beijing institute of vacuum heat treatment research, gas carburizing microputer control technology (Beijing university of aeronautics8 /