Large ring forging process
Large rings usually refer to metal rings with a diameter of more than 1m, such as rotary supports on port machinery and mining machinery, offshore wind power yaw rotor bearings, tower flanges, nuclear reactor shells, heavy carrier rocket fuel storage tank connection rings, etc., which are important parts in machinery, energy, national defense and other industrial fields. Due to the harsh working conditions, this kind of ring usually needs to have a high comprehensive mechanical properties, at present, the main method of forging production, that is, forging and then rolling forming, the main process is: blanking → heating → billet → (reheating) → rolling → heat treatment → mechanical processing, as shown in the figure.
Commonly used raw materials are continuous casting round billet, square billet, round ingot, round steel and large round corner square steel, etc. General raw materials need to be strictly inspected after entering the factory. The common cutting methods mainly include cutting by sawing machine (band saw, disc saw), electric discharge processing, gas cutting, and cutting by press after drawing the multi-angle ingot. Among them, the cutting of sawing machine is the most common application, and the specific cutting method should be reasonably selected according to the actual situation of cutting quality requirements, cutting cost, productivity and so on.
2.heat
Large ring forging is usually carried out in the hot forging temperature range, so the blank needs to be heated before forging. Heating methods usually include coal heating, gas (natural gas) heating, oil heating and electric heating, and the equipment used is generally rotary hearth furnace (ring furnace), chamber furnace, trolley furnace, etc. The selection of specific heating methods and equipment should consider many factors such as heating efficiency and quality, fuel supply, heating cost, and environmental pollution. In the rolling production of large ring forgings, due to the factors such as the connection control of the forming process and process, the capacity of the forming equipment and the layout of the workshop, it is necessary to use the reheating process when the temperature of the finishing ring is low or the distance between the forming and the rolling site is far. In addition, when the ring rolling machine with smaller tonnage is used to roll large size rings, if the ring billet temperature drops to a low value during the rolling process, it also needs to be reheated.
3.forging
Billet making is mainly to get ring billet for rolling by cutting, punching or reaming the solid billet after blanking. The billet making method is mainly free forging and punching. The precision and quality are poor, but the forming force is small, the requirement for equipment is low, and the application range is wide. The billet making equipment usually has a free forging hammer, hydraulic press and multi-station special hydraulic press, of which the special hydraulic press has higher billet quality and efficiency.
4.roll
Large ring rolling is usually carried out by radial axial rolling process on radial ring rolling machine. The hot ring billet is placed on the core roller by the manipulator. The core pulling methods of the core roller are usually upper core pulling and lower core pulling. The operator mainly controls the rolling process according to the target size and rolling curve. At present, most of the domestic ring rolling machines adopt manual or semi-automatic control mode, and the rolling process mainly relies on the operator to adjust the feed speed of the core roll and the cone roll and the rotation speed of the cone roll according to the real-time rolling state to ensure the stable rolling process until the final target size ring is obtained.
5.Heat treatment
The rolled ring is usually placed for a period of time before heat treatment (some ring parts are heat treated after rough turning). Heat treatment is mainly to change the material properties to meet the performance requirements of the product. The usual heat treatment methods include normalizing, quenching, tempering, etc., heating temperature, holding time, cooling speed are the three main factors affecting the quality of heat treatment, usually according to the material category and heat treatment method to find the heat treatment manual to determine. The heating during the heat treatment process is usually carried out in a resistance furnace to ensure the accuracy of the temperature; The cooling method is mainly air cooling, oil cooling or water cooling.
6.machining
The heat-treated ring is machined according to the size of the target part. For large ring parts, the cutting is usually carried out on a vertical lathe. Before cutting, the position of the ring needs to be adjusted to ensure the horizontal and radial neutrality of the axial height of the ring. Before the product parts leave the factory after machining, they also need to be inspected according to the user's inspection requirements, generally need to check the size of the ring, surface hardness and appearance, and carry out surface testing. For the ring parts required for dynamic performance and microstructure inspection, sampling and testing are usually carried out at the edges and corners of the forging during machining, and some products need to be fully profile tested according to user requirements.
