Comparison of welding rotors with other rotors

At present, there are three types of rotor structure in large nuclear power turbine, that is, whole forged rotor, set rotor and welded rotor.This article will introduce comparison of welding rotors with other rotors.

The following knowledge points are listed below:

Comparison of the advantages and disadvantages of the three rotors

Application comparison of three rotors

Comparison of the advantages and disadvantages of the three rotors

(1)     The advantages of the whole forging rotor are simple structure and good integrity, but the disadvantages of the whole forging rotor are the large size of the forgings, higher requirements on the forging technology and equipment, more complex process and quality inspection, large material loss.It is difficult to manufacture large integral forgings such as the low pressure rotor of a half speed turbine over 1000MW.At present, the nuclear steam turbine with this structure has been ordered and manufactured in China, but there is no precedent in the manufacturing technology of whole rotor forging blank in China.

(2)     Set rotor disc and shaft with a key connection interference fit, the disc and shaft are separately manufactured, the advantages of set rotor is small forging, easy to process.The disadvantage of set rotor is that the impeller hole stress is large, the set rotor rigidity is poor, in the process of high temperature operation, easy to make the impeller and spindle set loose phenomenon;Quick start is not adaptable.

(3)     The advantage of welding rotor is that the hollow cavity structure is relatively light in weight and large in rigidity, which is especially suitable for the requirements of large diameter and large weight of low-pressure welding rotor of nuclear turbine.Small size of piecewise forging, easy to process.The disadvantage of welding rotor is that the welding process requirements are high: the material of welding rotor is required to have good welding characteristics.

Application comparison of three rotors

Large nuclear power steam turbine rotor blank manufacturing technology, belongs to the key technology in the field of the steam turbine manufacturing, at present our country is still in its infancy, the domestic some large steam turbine manufacturing enterprise, the ongoing technological transformation and the introduction, million kilowatt nuclear power steam turbine low pressure welding rotor technical transformation project plan began to form in 2013, annual output of 5 root production capacity, millions of nuclear power suit welding rotor technical transformation project plan 5 root formation in 2011 the annual production capacity.

Among them, the welding rotor is the most representative. The high pressure welding rotor and low pressure welding rotor are very typical.Welding rotor of the low pressure cylinder all adopt the welding structure.The open cavity structure is designed for the short joints of each forging, which not only reduces the weight of parts and steel consumption, but also reduces the forging difficulty. At the same time, compared with the solid structure, this cavity structure is more conducive to ensuring the quality of welding.For millions of nuclear power turbines, each low pressure welding rotor has 11 annular welds, and each high pressure welding rotor has 3 annular welds. The requirement for welding technology is still very high, which is also the key point of welding technology.The precision of welding and the control of welding deformation are the difficulties in welding process.

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