Shaft Forgings for Hydraulic Turbines and Hydraulic Generators

1 Smelting

1.1  Alkaline electric furnace smelting should be used for forging steel.

2 Forging

2.1 Sufficient cutting allowance should be present at the upper and lower ends of the steel ingot to ensure that the forged piece is free from shrinkage cavities and severe segregation.

2.2 The forging equipment should have sufficient capacity to ensure complete forging throughout the section. The shape and dimensions of the forged piece should closely match the requirements of the finished product. The axis of the forged piece should preferably align with the centerline of the steel ingot.

3 Heat Treatment

3.1 After forging, the forged piece should undergo normalizing and tempering treatment, and if necessary, quenching and tempering treatment to obtain a uniform structure and properties.

4 Welding

4.1 Large axial welding should be carried out after the mechanical performance test of the forged piece meets the requirements. Welding electrodes with equivalent mechanical properties to the forged piece should be used, and the best welding specifications should be chosen for the welding process.

5 Technical Requirements

5.1 Chemical analysis should be conducted for each batch of molten steel, and the analysis results should comply with relevant specifications.

5.2 After heat treatment, the axial mechanical properties of the forged piece should meet the relevant specifications. If required by the customer, additional tests such as cold bending, shearing, and nil-ductility transition temperature can be performed.

5.3 The surface of the forged piece should be free from visible cracks, folds, and other appearance defects that affect its use. Local defects can be removed, but the depth of removal should not exceed 75% of the machining allowance.

5.4 The central hole of the forged piece should be inspected visually or using a boroscope, and the inspection results should comply with relevant specifications.

5.5 Ultrasonic testing should be performed on the body and welds of the forged piece.

5.6 Magnetic particle inspection should be conducted on the forged piece after the final machining, and the acceptance criteria should comply with relevant specifications.