核电AP1000钢制安全壳与附件焊接性及焊接工艺研究

发布时间：2018-06-02 18:18

本文选题：SA738Gr.B钢 + AP1000核电　；参考：《太原理工大学》2015年博士论文

【摘要】：低合金高强钢SA738Gr.B与双相不锈钢S32101首次应用于三代核电AP1000建设中。SA738Gr.B主要用于钢制安全壳拼焊，与混凝土安全壳一起组成核电安全的最后一道屏障。S32101双相不锈钢主要应用于结构模块，，而且要和硼酸介质接触，对强度及耐蚀性有较高的要求。研究两种钢材的焊接性能，保证接头在服役过程中具有良好的性能是本研究的重要任务。本研究采用热模拟的方法测定并绘制了SA738Gr.B的SHCCT转化曲线。结果表明：随着冷却速度的降低，热影响区组织将先后发生贝氏体、贝氏体+先共析铁素体、贝氏体+先共析铁素体+珠光体的组织转变，硬度相应降低。采用Gleeble-1500试验机模拟了热影响区，分析了焊接HAZ的过热区，正火区，不完全正火区组织、冲击韧性的变化和多层多道焊时的热影响区组织变化。焊接过程中当t8/5的数值在10-15秒时，其冲击韧性值最佳。为研究其热影响区组织的变化规律提供了依据。通过斜Y坡口抗裂性试验和插销试验及Z向拉伸试验方法分析了SA738Gr.B钢板的焊接性。斜Y坡口试验证明，当预热温度超过100℃，接头无裂纹产生。该钢具有较高的抗Z向冷裂性能，Z向抗裂性试验的断面收缩率大于35%。插销试验在预热和不预热的条件下，粗晶区的抗强度均大于钢材的最小抗拉强度，表明粗晶区亦具有较好的抗冷裂性能，SA738Gr.B具有较好的焊接性。研究了低合金钢SA738Gr.B配套专用焊材，成功研发了铁粉型焊条E9018-G-H4和ER90S-G焊丝。通过实验研究证实，当铁粉含量在15%且碳酸钙-萤石比例为1.6:1左右时，焊条具有较好的工艺性能和良好的力学性能。研究了实芯焊丝熔敷金属碳当量和合金元素对焊缝力学性能的影响。结果表明，随着碳当量的提高，熔敷金属抗拉强度和屈服强度提高。Ni元素显著影响熔敷金属的低温冲击韧性，当镍元素含量在1%左右时其低温冲击韧性较高。该种焊条已经应用于AP1000钢制安全壳的焊接，使用量已达320吨。在钢板焊接性及焊材研究的基础上进行了接头力学性能的研究。研究表明，焊接线能量对接头的冲击韧性有着显著影响。随着线能量的增加，冲击韧性值先增加后减小。SA738Gr.B钢板合适的工艺是预热+小线能量。焊后热处理对接头的性能有重要影响，在热处理过程中，接头会发生回复和再结晶等变化。随着热处理时间的延长，晶粒有长大的趋势，碳化物等向晶界析出，晶内位错密度下降，造成其冲击韧性下降。现场的工程实践表明，研制的焊接材料和依据本研究结果确定的焊接工艺均可满足SA738Gr.B核电安全壳的技术要求，焊接质量达到ASME III和技术条件的要求，获得了国内外同行的认可。双相钢焊接对线能量敏感，出现热影响区韧性降低及耐蚀性能下降。通过固溶处理可完全恢复韧性及耐蚀性能，甚至可达到与母材相接近的程度。为进一步研究温度对双相钢接头的影响，将固溶处理后的接头在500℃、600℃、700℃、800℃、900℃下分别时效30min，测试结果表明，冲击韧性和耐蚀性随时效温度增加先降低后增加，700℃是S32101双相不锈钢焊接接头性能恶化的最敏感温度。S32l0l不锈接头进行700℃时效处理结果表明，Cr2N在晶内析出及生长，造成贫铬的二次奥氏体是造成塑性、韧性降低和耐腐蚀性能的根本原因。现场的工程实践表明，研制的焊接材料和依据本研究结果确定的焊接工艺均可满足AP1000核电安全壳的技术要求，焊接质量达到ASME III和技术条件的要求，获得了国内外同行的认可。
[Abstract]:Low alloy high strength steel SA738Gr.B and dual phase stainless steel S32101 are first applied to the three generation nuclear power AP1000 construction..SA738Gr.B is mainly used for the welding of steel safety shell. The last barrier of nuclear safety with concrete safety shell,.S32101 double phase stainless steel is mainly applied to the structure module, and it should be contacted with boric acid medium, strength and resistance. It is important to study the welding properties of the two steels and ensure the good performance of the joints during service.
In this study, the SHCCT transformation curve of SA738Gr.B was measured and plotted by the method of thermal simulation. The results showed that with the decrease of cooling rate, the microstructure of the heat affected zone would occur successively, bainite + pre eutectoid ferrite, bainite + pre eutectoid and pearlite, and the hardness correspondingly decreased. The Gleeble-1500 test machine die was adopted. The heat affected zone is proposed, and the microstructure changes of the superheated zone, the normalizing zone, the incomplete normalizing zone, the impact toughness and the heat impact zone during multi-channel and multi pass welding of the welded HAZ are analyzed. In the welding process, when the value of t8/5 is 10-15 seconds, the impact toughness is the best. It provides a basis for the study of the change law of the microstructure in the thermal shadow zone.
The weldability of the SA738Gr.B steel plate was analyzed by the slanting Y slope crack resistance test, the bolt test and the Z tensile test. The slanting Y slope test proved that the joint had no cracks when the preheating temperature was over 100 C. The steel had a high anti Z cold cracking performance, and the fracture surface shrinkage rate of Z to crack resistance test was greater than that of the 35%. bolt test in preheating and not preheating. Under the heat condition, the strength of the coarse-grained region is greater than the minimum tensile strength of the steel. It shows that the coarse-grained region also has good cold cracking resistance, and SA738Gr.B has good weldability.
The special welding material for SA738Gr.B of low alloy steel was studied. The iron powder type welding rod E9018-G-H4 and ER90S-G welding wire were developed successfully. Through the experimental study, it was proved that the electrode has good technological properties and good mechanical properties when the content of iron powder is 15% and the ratio of calcium carbonate fluorite is about 1.6:1. The effect of alloy elements on the mechanical properties of the welding seam shows that with the increase of carbon equivalent, the tensile strength and yield strength of the deposited metal can significantly affect the low temperature impact toughness of the deposited metal. When the nickel content is about 1%, the toughness is higher at low temperature. The welding rod has been applied to the welding of the AP1000 steel shell. The amount of use has reached 320 tons.
The mechanical properties of the joint are studied on the basis of the weldability and welding material of the steel plate. The study shows that the welding line energy has a significant influence on the impact toughness of the joint. With the increase of the line energy, the appropriate process of the.SA738Gr.B steel plate is preheated and the small line energy is reduced with the increase of the line energy. In the process of heat treatment, there will be a change of recovery and recrystallization in the process of heat treatment. With the prolongation of the heat treatment time, the grain has a tendency to grow up, the carbide precipitates to the grain boundary, and the intragranular dislocation density decreases, resulting in the decrease of the impact toughness.
The field engineering practice shows that the welding materials developed and the welding technology determined according to the results of this study can meet the technical requirements of the SA738Gr.B nuclear safety shell, and the welding quality meets the requirements of ASME III and technical conditions, and it has obtained the approval of the domestic and foreign counterparts.
The dual phase steel is sensitive to the line energy, and the toughness and corrosion resistance of the heat affected zone are reduced. The toughness and corrosion resistance of the heat affected zone can be recovered completely by the solution treatment. It can even reach the degree of close to the parent material. In order to further study the effect of temperature on the double phase steel joint, the joints after the solution are at 500, 600, 700, 800, 900. The results show that the impact toughness and corrosion resistance increase first and then increase with the increase of aging temperature. The 700 C is the most sensitive temperature of S32101 double phase stainless steel welded joint,.S32l0l non rust joint,.S32l0l stainless steel joint carried out at 700 C, indicating that Cr2N is precipitated and grown in the crystal, resulting in two austenite of poor chromium. The root cause of plasticity, ductility reduction and corrosion resistance.
The field engineering practice shows that the welding materials developed and the welding technology determined according to the results of this study can meet the technical requirements of the AP1000 nuclear safety shell, and the welding quality meets the requirements of ASME III and technical conditions, and it has obtained the approval of the domestic and foreign counterparts.
【学位授予单位】：太原理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG457.11

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