Large-scale cake forgings are one of the core parts of heavy equipment, including tube plate and impeller of steam turbine boiler, flat cap of nuclear reactor pressure shell, heat exchanger tube plate, chemical container seal first class, and some have blind hole. All the raw materials used are ingot. Ingot has its inherent defects, such as segregation, inclusions, loose, coarse columnar crystals and so on. In order to reduce these casting defects, on the one hand to improve the level of smelting, on the other hand to improve the level of forging, only in order to produce high-quality forgings. The production process of cake forgings is generally as follows: Large hot steel ingot is sent to the hydraulic press workshop, forged into forgings by a series of forging process, and sent to the next process after heat treatment for machining and final heat treatment. The conventional forging process is: Ingot → chamfering (pulling long), blanking → flat upsetting (or flat upsetting + local upsetting) → finished product. Their contour size is characterized by a h/d ratio of more than 1. This kind of forgings are made by upsetting, which requires high quality, and the process is not high in ultrasonic flaw detection.
In the actual production, the scrap rate is high, the production is difficult, the most serious is the layered crack problem.
The forging process to overcome the layered defects is mainly as follows: First, conical plate upsetting process. This process can be used in electric furnace smelting, vacuum pouring or pouring in the atmosphere ingot.
Ingot chamfering, pre-pulling long blanking, and then after heating with the upper and lower conical plate upsetting. Second, the forging process of controlling the inclusion crack. The purpose of this process is to control the internal quality of forgings in the process of forging, in addition to the external dimension precision of forgings.
In the process formulation of large-scale cake forgings, in addition to the conventional forging process to determine part of the process parameters, but also should follow certain criteria. Third, the pressure-nest forming method. The tool used in the forging process is still a flat anvil, a lower turntable and a solid punch. The tools used to crush the nest are extremely simple. It is a kind of punching (hollow punch) which can be found almost at the working site of any hydraulic press, so long as its diameter is suitable for selection. The forging method first presses a nest in the center of the cake-shaped forgings, then rotates the flattening, flips to the other side, presses the nest again, and then rotates the flattening to produce the finished product.