Die Preforming Process: Long Last-stage Blade Nuclear Power

founder Preforming Process Long Last-stage sword Nuclear PowerDesign and Optimization of Die Preforming Process for Long Last-stage Blade of Nuclear PowerHe Xiaomao1,aJiang Peng1, Lin Jingtang2Huang Jianning11 Beijing Mechanical and Electrical Institute of TechnologyBeijingmain pull down China2 Tian Qian Heavy Industry Company, Ltd, Mianzhu, SiChuan, ChinaAbstract The long last-stage blade is a key component of the steam turbine of nuclear conventional is acres. The give out preforming exercise for a new technology that provides billets for near-net-shape roll-forge sue was designed, the effects of the beat temperature, friction coefficient, photograph lands line of longitude and starts out taenia radius on the take place hammer military shove and forging energy were burnvas by using the orthogonal experiment method, the primary and secondary order of the four factors were analysed by using enjoin analysis method, and the best combination of the factors was obtained . By means of numerical simulation and physical experiment, the kick downstairs preforming process that batch provide qualified billets for the subsequent roll-forging process was verified, and the PZS1120f electric jazz press can meet the requirements of the die preforming process.1 PrefaceThe long last-stage blade is the key component of the steam turbine of the nuclear power conventional island. The larger the exhausting theatre of operations of the last-stage blade of the LP cylinder is, the higher the efficiency of the nuclear power unit is and the better the economy is 1. Harbin Steam Turbine factor iny had successfully developed a 72-inch (1829mm) half-speed nuclear power turbine blade 2, Shanghai Electric had also developed a 67-inch (1710mm) nuclear power blade 3, the development of these long blades effectively improves the efficiency of nuclear power unit, but its also a challenge to manufacture these long last-stage blades. At present, the technology of preforming a nd overall forging was mainly adopted by the domestic help and foreign blade manufacturers 4, 5. The radial forging and the open-die forging was adopted respectively by the foreign and domestic blade manufacturers as blanking process, and then, the overall die forging process was adopted to form the blades. Due to the large area of these blades, the capability of the blade manufacturers forging equipment cannot meet to the required forging disembowel of producing the blades and the forged blades had got almost defects, such as underpressing, underfill and overweight. The die preforming process that provides billets for a new near-net forming process for nuclear last-stage blades was proposed, the new process, which uses the roll-forging process to form the blade body of the long blades, the die forging to form the blade root, coronate and damper, can effectively reduce the required forging force. In this paper, the die preforming technology of long last-stage blade was designed, the process parameters were optimized by the orthogonal experiment method and numerical simulation, and the feasibility of the process was verified by physical experiments.2Optimization of process parametersThe die preforming process was carried out in the PZS1120f type of electric screw press, the nominal tonnage duty of the press is 250,000 kN. According to the nominal tonnage, the maximal projection area of the forging billet was calculated. The forging force is not only related to the material and forgings projection area, but also related to the strain rate, temperature, friction coefficient and die structure ( point of the flash land and the outer fillet radius of dies). Because the strain rate is related to the forming speeding of the press, its value is resolute when the forging press is chosen. The forging temperature, the friction coefficient, the height of the flash land and the outer fillet radius were chosen as the process parameters to be optimized and the forging f orce and forging energy were chosen as optimization objectives.2.1 Die preformed forging and dies3D stupefy of a preformed forging was memorializen in nameure 1, the forging model was calculated based on the press nominal tonnage and the forging drawing of the 72-inch blade, the calculation process wasnt repeated here, it will be discussed in detail in the future article. The dies structure was shown in Figure 2, it didnt take for the groove of the flash, and the structure was quite simple, only the height of the flash land h and the outer fillet radius r were con gradientred as parameters.Figure. 1 3D model of die preformed forging Figure. 2 Die Structures Figure. 3 Billet of the die preforming2.2 Levels and factors flurry of orthogonal experiment external experiment method can be used to study the impact of multiple factors on the optimization objective by less number of trials, to obtain the best combination of factors for the optimum objective value. The forging force and t he forging energy of the die preforming are related to the forging temperature A (T), the friction coefficient B (), the height of flash land C (h) and the outer fillet radius D (r). The four parameters were adopted as the orthogonal experiment factors, each factor took three levels, and the designed factors and levels table were shown in Table 1.Table 1. Factors and levels table of the orthogonal experiment.FactorLevelAForging temperature T/BFriction coefficient Cheight of flash land h/mmDouter fillet radius r/mm111800.262211500.383311200.41042.3 Parameter settings of numerical simulationThe billets used in the die preforming were produced in the semi-open heading process in ref. 6. The shapes and dimensions were shown in Fig 3. The material is 1Cr12Ni3Mo2VN, and the constitutive relation of the material was from ref. 7, in the Arrhenius form and the hyperbolic sinusoidal was used. 1The die was modeled as a rigid model with a preheat temperature of 200 C and a forming speed of 400 mm / s. The forging temperatures and the friction coefficients were set according to Table 1.2.4 takingss oforthogonal experimentOrthogonal experiments were performed using the 3-level and 4-factor table L9 (34) 8, without considering the interaction between the factors, the orthogonal experiments of simulation arrangement and the cores were shown in Table 2.Table.2 orthogonal experiments of simulation arrangement and the resultsNO.FactorResultABCDForging Force FkNForging Energy EkJForging temperatureFriction coefficientFlash land heightOuter fillet radius1113234300058302121146200062003132344900064404212139800064205223336400065106231263100073707311352200072708322246500073709333142700074402.5 Range analysisThe value of Kjm was the sum of the result of the m factor at j level, and the means were represented by kjm, the value of kjm can reflect the optimal level. Rm was the range of the mth factor, the value of Rm reflected the fluctuation range of the optimal objective when the m f actor fluctuated, the bigger the Rm was, the greater the make for of the m factor on the objective was. The primary and secondary order of the factors can be judged according to the range. The results of the range analysis of the forging force F and the forging energy E were shown in Table 3.Table.3 Range analysis of the forging force F and the forging energy EResultFactorABCDForging Force FkNK1m12540000126300016150001287000K2m13930000129100013120001439000K3m14140000150700011340001335000k1m4180000421000538333.3429000k2m464333.3430333.3437333.3479666.7k3m471333.3502333.3378000445000Rm53333.381333.3160333.350666.7OrderCBADForging Energy EkJK1m18470195202084020060K2m20300200802023020570K3m22080212501978020220k1m6156.76506.76946.76686.7k2m6766.76693.36743.36856.7k3m73607083.36593.36740Rm1203.3576.7353.3170OrderABCDAccording the range of forging force in Table 3, the order of importance that the factors influences the forging force were the height of flash land C, the coefficient of fri ction B, the forging temperature A, the outer fillet radius D. According to the range analysis, the optimal combination to obtain the minimum forging force was (C3B1A1D1). The relationships among the forging force and the factors were shown in Figure 4, forging force decreased with increasing temperature, with decreasing of friction coefficient, and with increasing of the flash lands height the relationship between forging force and the outer fillet radius didnt show significant trend of increasing or decreasing, but the range was the smallest among the four factors.Figure. 4 familys among the forging force and factorsAccording the range of forging force in Table 3, the order of importance that the factors influences the forging energy were forging temperature A, friction coefficient B, height of flash land C, outer fillet radius D. Except the forging temperature can cause some fluctuations of the range of forging energy, the effects of other factors on the forging energys fluctuat ion were quite small, because the heating temperature made the transition of watch glass atoms more easily, macroscopically indicated that the metal was more easily deformed, and the temperature increasing weakened the third-phase particles on pinning the dislocation movement, the required deformation energy was smaller And the tranquility factors didnt suck effects on the atomic migration and dislocation movement, and the macro behavior was that the forging energy didnt fluctuate obviously.3 Numerical simulation analysesAccording to the optimizing result of the orthogonal experiment, the parameters were forging temperature was 1180 , friction coefficient was 0.2, flash lands height was 10mm, and outer fillet radius was 3mm, and the other parameters were same as orthogonal experiment. The simulation results were shown as followsFigure.5 Relationship between stroke and forging force and energyAs shown in figure 5, the predicated forging force was 304000 kN and the forging energy wa s 5680 kJ by using the optimal scheme. Compared with the result of orthogonal experiment, it was found that the value simulated by the optimal factor and level combination was the smallest one.Even if the optimal scheme was utilized, the forging force of 304,000 kN was great than the nominal tonnage 250,000 kN of PZS1120f electric screw press. In the live production, there would be some issues, such as the upper and lower die cannot be clamped, the forging would be underpressing and underfill. However, in order to ensure that forged billet has enough width and a certain length, to minimize the deformation on the width direction during the roll forging step, a few underpressing in the height direction would be allowed. The situation of die cavity filling maculation the forging force was 207000kN was shown in Figure 6, except the crown part of the outlet side, the rest of the billet was almost filled, and the value of underpressing of the dies was 2.7mm, this underpressing value wou ld not have too much impact on the roll-forging of the blade.Figure.6 Situation of die cavity filling while the forging force was 207000kNThe reason that cause the outlet side of the crown was not filled was the billet deflected to the inlet side at the beginning of the forging (as shown in Fig. 7), resulting in a shortage of material on the outlet side and the flash at inlet side was too large (Figure 6).4Die preforming experiment Figure 8a were the upper and lower die used for the die preforming experiment, and Figure 8b is the blank, which was the forging in the heading experiment. Heating temperature was 1180 , die preheating temperature was 200 , lubricated by graphite emulsion lubricant, and dickens blanks were forged in this experiment.The work force was set to the nominal tonnage of PZS1120f electric screw press, during the forging process, the first blow was to locate the blanks position and to remove the scale, and then, the blank was forged by the next two blows. The fi nal forging forces of the two forged parts were measured to be 223460 kN and 213690 kN respectively. The die preforming forgings were shown in Figure 9, two forgings had varying degrees of underpressing and underfill, the underfill of the crown part at the outlet side was more serious, and the flash at the inlet side was much large. With numerical simulation results, it can be determined that the reason of these defects was the blanks deflection to the inlet side some measures should be taken to prevent the blank deflection in the live production.The flash lands heights of the two forgings were measured to be 12.9mm and 12.8mm, the values of underpressing were 2.9mm and 2.8mm, because the forging force had reached the maximum tonnage of the press, its hard to clamping the upper and lower die by increasing the number of blows, and it would handicap the press and dies. These defects can only be solved by the subsequent roll-forging process.a) Upper and lower dies b) heading billetsFi gure.8 Dies and billets of the die preforming experiment Figure.9 Die preforming forgingsThe feasibility of the die preforming process was verified by the experiment, and the PZS1120f electric screw press can basically meet the requirements of die preforming process, and the qualified billets can be provided for the subsequent near-net-shape roll-forging process.5 ConclusionsThrough the orthogonal experiment optimization, numerical simulation and physical experiment, the following conclusions can be drawn1) Among the four factors Forging temperature A, friction coefficient B, flash lands height C and the outer fillet radius D, the principle factor that impacts on forging force was the flash lands height, and the forging temperature had some effects on the forging energy, the optimal factor and level combination was C3A1B1D1.2) The qualified billets formed by die preforming process can be provided for the subsequent near-net-shape roll-forging process and the PZS1120f electric screw press basically meets the requirements of the process.3) The billet was deflected during the forging process, resulting in the underfill of the crown part at the outlet side, some measurements should be taken to prevent the deflection in the live production.ReferencesT. 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