Generator Rotor with stands the huge centrifugal force generated by high-speed rotation while working, and also withstands torsional and bending stresses. Therefore, it is required to have high strength, good toughness, uniform tissue performance and low residual stress. In order to ensure the above performance requirements, the general rotor materials are: 34CrMo1A, 34CrNi1A, 34CrNi2A, 34CrNi3A, 25CrNiMoV, 33CrNi4Mov, etc.With the continuous increase of single generator capacity of large generators, the rotor forgings are also correspondingly large-scale development. In order to ensure the quality of forgings, the size of steel ingots also tends to be large. It can be seen from the analysis of power station accidents that the cause of rotor fracture is In addition to stress concentration, low lateral plasticity in the rotor center and high brittle transition temperature, there are mainly a lot of metallurgical defects such as inclusions and looseness in the rotor, and even some white spots. Therefore, the content of S, P and other harmful elements is strictly controlled during smelting of steel ingots. The content of S and P should be controlled below 0.01%~0.015%, and the content of H2 in steel should be less than 2/100g. Take protective measures for pouring to reduce the content of harmful gases and reduce the degree of looseness.
■ 1000 MW Generator Rotor
25Cr2Ni4MoV , the maximum diameter of the rotor is 1275mm, the length is 10665mm, and the forging weight is 67.97t.Brand: CITIC, HENGIN.
■ Chemical composition of materials
| C | Si | Mn | P | S | Cr | Ni | Mo | Cu | V | Al | As |
| ≤0.34 | ≤0.37 | ≤0.47 | ≤0.012 | ≤0.012 | 1.45~2.05 | 3.18~4.07 | 0.18~0.52 | ≤0.35 | 0.07~0.17 | ≤0.015 | ≤0.02 |
■ Mechanical Property
| Sampling location | Rp0.02 /MPa | Rm /MPa | A(%) | Z(%) | Akv/(J·cm-2 ) | FATT50 /℃ | |
| Body radial | within | ≥690 | ≥690 | ≥690 | ≥690 | ≥690 | ≤-10 |
| External | ≥690 | ≥690 | ≥690 | ≥690 | ≥690 | ≤-10 | |
| Center Hole | ≥690 | ≥690 | ≥690 | ≥690 | ≥690 | ≤-10 | |
Brittle transition temperature of materials.
■ The main production process of rotor forging
primary refining of electric furnace - LF refining - VCD treatment - lf heating - VC pouring - hot delivery of ingot - ingot heating - press forging - post forging heat treatment - Roughing - performance heat treatment - semi finishing - ultrasonic flaw detection - Sampling Test - finishing - magnetic particle inspection - final inspection - delivery of finished products.
■ Flaw detection requirements
ultrasonic flaw detection shall be in accordance with the requirements of rotor of steam turbine and generator.The ultrasonic flaw detection shall be carried out; the magnetic particle flaw detection shall be carried out in accordance with the requirements of steam turbine and generatorMagnetic particle testing of motor rotor.
■ Technical requirements
◆ chemical composition: the analysis results of finished products of chemical composition shall meet the requirements.◆ Grain size: the grain size shall not be lower than grade 5 of ASTM standard, grade 4 is allowed, and the total amount shall not exceed 5%.
◆ mechanical properties: radial tensile strength or yield of each forging.The fluctuation value of strength shall not exceed 40MPa, and shall meet the requirements. The yield strength value of 0.2% deformation shall also be tested and reported.
