Research On The Expanding Technology Of Tube To Tube Sheet For 300MW Nuclear Power Station Steam Generator

China has the proprietary intellectual property rights in the design and manufacture of 300 MW nuclear power station steam generator. The expansion method used in the tube to tube sheet expanding joints of 300 MW nuclear power station steam generator is interval mechanical expansion, which is quite different from the hydraulic expansion used in the popular and advanced second generation steam generator. The interval mechanical expansion method has been widely used in the tube to tube sheet manufacturing process of low power nuclear power station steam generator for its advantages such as the simple operation,convenience and high reliability etc.The thesis gives a theoretical introduction and calculation to the technology of interval mechanical expansion, analyzes the influence of the expansion joint power, friction coefficient and tube thickness on the mechanical expansion method and confirms the items to be verified; measures the expansion size and the length of un-joint part of the secondary side,calculates the expansion joint power, checks the surface of joint and tests the pull-out power,tightness, profile, residual power. Comparing the test results with the calculation, the best expending parameters have been gained. The main research results are as followed:The experimental results satisfy the standard of the product and theoretical values calculated under the given conditions according to calculation of pre-expanding and post-expanding actual measurement values. The pull-out power increases correspondingly with the expanding power increasing and meets the theoretical analysis that pull-out power has a linear relationship with the expanding residual stress and expending joint power. The test result is much less than the max theoretical pull-out data getting from the tube ultimate tensile calculation,so it could make sure the setting expending joint power is appropriate.Testing the residual stress for the heat exchange pipe with the full release method, it could be known that the residual stress exists in the expanding area, transition area and no expansion area in different degree. The surface stress in the original no expansion tube is minor, but in expanding area and transition area is very significant.The sealing experiment has been checked under 12.75MPa, that's all right; then the maximum bearing capacity in 25Mpa water pressure in running conditions has been checked,there is no leakage in the first 3.5 hours. All above proves that the mechanical expending used in the 300 MW nuclear power station steam generator is reliable.Seen from the cut sample, there is no harm on the inner wall of the exchange heat tube after the positioned expansion, primary side expansion and the secondary side expansion; the transition area are smooth and evasive; un-joint part of the secondary side length in magnification satisfy the recommend value of 4±1mm. So the expansion technology could agree with the product's expansion requirements.