Forging molding process for integral hollow nuclear power main pipe

Abstract

The invention discloses a forging molding process for an integral hollow nuclear power main pipe. The process includes steps: placing a TP316LN stainless steel hollow electroslag casting into a heating furnace to realize primary heating and heat insulation; secondarily heating after the heat insulation procedure is completed; thirdly heating after the secondary heating is completed; and forging after the third heating is completed. The forging procedure includes repeated drawing-out, necking and branching, then secondary drawing-out, tube blank molding and finally tube nozzle drawing-out and hole punching, When the temperature of a forged part is reduced to 880 DEG C during forging, the forged part needs to be returned to the furnace to be heated at a heating speed close to the temperature rise speed of the power of the heating furnace, and the temperature is kept. By the aid of the process, manufacturing cost of the nuclear power main pipe can be lowered, and the problems that the grain size is large and forging and heating are controlled difficultly due to the fact that 316LN stainless steel is austenite stainless steel and does not have allotropic transformation can be solved.

Description

technical field [0001] The invention relates to a forging process of pipe fittings, in particular to an integral hollow forging forming process of a nuclear power main pipeline. Background technique [0002] The AP1000 forged main pipe is a major first-level equipment of the nuclear island. The main pipe is integrally forged with 316LN stainless steel, and welding is not allowed. In terms of forging and forming technology, solid steel ingots are used for solid forging on 10,000-ton presses at home and abroad at present, and the inner hole of the main pipe φ786 is not forged. This not only wastes expensive raw materials, but also is completely machined. The method of drilling deep holes removes more than 20 tons of inner hole material, which greatly increases the processing time, greatly prolongs the manufacturing cycle, and also greatly increases the manufacturing cost of pipe fittings. Due to the limitation of the capacity and cost of the electroslag remelting furnace, th...

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Problems solved by technology

[0003] The purpose of the present invention is to overcome the defects in the prior art and provide a large-scale ultra-low carbon and nitrogen-controlling 316LN stainless steel forging that meets the technical requirements of AP1000 and adopts a hollow steel ingot integral hollow forging molding process, which can reduce the cost of nuclear power main pipelines. The manufacturing cost can also solve the problem that 316LN stainless steel is austenitic stainless steel without allotropic transformation, and it is difficult to control forging and heating in order to prevent the grain size from growing.

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