Sheet Metal · 2021年12月4日

Shaft machining process for steam turbine generator shaft

Turbine generator shaft processing technologies include many: shaft forging inspection and cutting tests, turning technology, milling technology, boring technology, etc. There are certain requirements for use in materials for rotating shafts. Let’s introduce each of these contents individually.

The material of the rotating shaft

Large capacity turbine rotor cores are made of high quality alloy steel forgings with high mechanical strength and permeability (nickel-chromium-molybdenum-vanadium, nickel-chromium-vanadium, vanadium-nickel-molybdenum, etc.) .. For large steam turbine generators in thermal power plants, most of the rotor shafts for large and large steam turbine generators at home and abroad, such as motor shafts that require load changes and frequent start and stop during operation, are NiCrMoV. Uses steel material.

The shaft machining process

The main processes of rotary shaft machining are as follows.
Shaft boring process Processing for crushing sequences, ordering processing and rotating shaft forging and tangential pivot shaft to confirm rotation again.

1. Rotating shaft forging inspection and cutting

After the rotary shaft forging is put into the factory, it shall be inspected strictly in accordance with the design drawings and related technical specifications. All information provided by the supplier must be complete and unsatisfactory forgings cannot be put into the cutting and processing process, which is harmful to the original condition.

First, clean the surface of the forging oil and the center hole with cleaning oil (kerosene), cotton thread, white cloth, etc. Check the center hole with a sniffer. The hole in the center must meet the requirements of the drawing. Second, custom specifications are required to perform ultrasonic flaw detection on the outer circular surface and other parts. The excess part of the journal part is the inner fillet magnetic particle inspection and surface hardness respectively. If all of the above items pass the inspection, a 350t sturdy CNC bed will rotate with a forged rotating shaft. Check the shape tolerance and machining allowance of each part of the forged product, and if it passes the test, cut the test ring according to the drawing and technical specifications.

2. Rotation axis rotation sequence processing technology

Machining of the axis sequence is performed on a heavy duty 350t heavy duty CNC sleeper. Currently, the traditional process for machining the rotating shaft of a steam (gas) wheel generator is as follows: Universal joint-double bracket support. That is, torque is transmitted by universal joints and the center frame is supported by rotating shaft steam, excitation journals, or oil slings. Using this processing technology, the adverse effects on processing accuracy due to factors such as gaps in the transmission mechanism of the machine itself can be sufficiently resolved.

3. Rotating shaft milling technology

The lower slot milling process uses a disc mill to perform rough and semi-finish milling, lowers the slot, and finishes the lower slot with a rod mill. The numerical control index accuracy of the device is used to ensure the index accuracy of the lower wire slot.

The rotor slots of a turbine generator are machined using a machine clamp welded rotor milling cutter. Due to the long grinding time of the milling cutter and the short grinding time of the rotor milling machine, the tool preparation is not connected and the machine tool often fails and cannot meet the production needs. In recent years, rotor rough cutting cutters that can index mechanical clamps and high-speed steel integrated milling cutters have been adopted. Indexable rotor milling cutters are used to improve production efficiency and ensure rotor groove machining quality.

4. Rotating shaft boring sequence machining process

A coupling drilling die is installed and the drilling die is assembled on the inner edge of the coupling end face. The model “A” mark is placed so that the outer circle mark “G” is symmetrical when the coupling is placed on the lathe. After assembly, the 0.02 mm joint surface should be free of tentacles. Then the main shaft of the boring machine can be found in the boring hole. When the coaxiality is within 0.01 mm, the coupling hole can be machined.

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