CLAM钢焊接接头在液态铅铋合金中的空泡腐蚀研究

发布时间：2018-03-16 09:35

  本文选题：铅铋共晶合金　切入点：空泡腐蚀　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：铅铋共晶合金(lead-bismuth eutectic,LBE)是加速器驱动次临界系统(Accelerator driven sub critical reactor system,ADS)和铅冷快堆(Lead cooled Fast Reactor,LFR)中重要的冷却剂候选材料,同时也是ADS系统的散裂靶候选材料。ADS系统中许多结构部件如核主泵叶轮、管道拐弯处、管道过流部位的接合处,都采用熔化焊的方法进行制造与装配。而这些部位在与液态铅铋合金做高速相对运动时,表面局部区域会产生压力突变区,引起气泡的形成与溃灭,造成比较严重的空泡腐蚀。CLAM钢是中国自主研发的低活化铁素体/马氏体钢(RAFM钢),是ADS系统与未来核电领域聚变示范堆的首选包层结构钢。焊态下CLAM钢焊缝组织主要为粗大、不均匀的板条马氏体,在整个ADS冷却回流管道中属于薄弱区域。因此研究CLAM钢焊接接头在液态铅铋合金中的空泡腐蚀可以为ADS系统及未来聚变示范堆能够更加经济、安全地应用提供理论基础。本文首先利用手工TIG焊的方法,切割同批次CLAM钢母材为填充材料,对5mm厚CLAM钢板进行平板对接焊,然后自主设计液态金属空泡腐蚀装置,将CLAM钢焊缝与母材两组试样在550℃液态LBE中分别进行不同时间的空泡腐蚀实验。对不同时间空泡腐蚀后的各组试样的表面形貌、相同面积内空蚀坑平均深度及表面粗糙度进行分析,并且结合各组试样的金相组织及力学性能研究其母材和焊.缝在液态铅铋中的空泡腐蚀过程、腐蚀机理及耐蚀性差异。结果表明CLAM钢焊缝与母材的表面粗糙度与平均腐蚀坑深度随着空泡腐蚀时间的延长一直呈现加速上升趋势,焊缝试样在液态铅铋中的空泡腐蚀过程仅为孕育期与加速期。在空泡腐蚀过程中,母材表现出的耐空蚀性能要大大优于焊缝。通过进行焊缝试样研究焊缝试样相同时间空泡腐蚀与静态腐蚀后试样截面的元素变化情况,发现液态铅铋合金中,溶解与氧化腐蚀和空泡腐蚀会互相促进,其联合作用会很大程度的破坏试样表面,这也是液态LBE中空泡腐蚀过程为孕育期、加速期的主要原因。由于焊后热处理是提高焊缝各项性能最直接且最有效的方法,且不同的焊后热处理方式会获得不同力学性能的焊缝,因此本文制定了4种不同的焊后热处理方案,研究其对CLAM钢焊缝耐空蚀性的影响。试验结果表明:调质处理后,CLAM钢焊缝恢复至细小均匀的回火马氏体组织,无δ铁素体,且其综合力学性能恢复至母材水准,耐空蚀性能最好。不同温度的高温回火后,其耐空蚀性都得到不同程度的改善,760℃回火后耐空蚀性能最好,其在极大提高焊缝的冲击韧性时,还保留较高的表面硬度与抗拉强度,综合力学性能比较好。而710℃与810℃高温回火后,其综合性能都有欠缺,耐空蚀性能次之。推荐焊后回火工艺为:760℃保温1h。
[Abstract]:Lead-bismuth eutectic LBEs are important coolant candidates for accelerator driven sub critical reactor systems and lead cooled Fast ReactorLFRs. At the same time, it is also the candidate material for spallation target of ADS system. Ads system has many structural components such as the impeller of nuclear main pump, the bend of pipeline, and the junction of pipeline flow. All of them are fabricated and assembled by melting welding. When these parts are moving at high speed with liquid lead-bismuth alloy, there will be a pressure abrupt zone in the local area of the surface, which will cause the formation and collapse of bubbles. The relatively serious cavitation corrosion. Clam steel is a low-activated ferrite / martensite steel RAFM steel developed by China, which is the preferred cladding structure steel for ADS system and future nuclear power field fusion demonstration reactor. The weld structure of CLAM steel under welding condition is mainly coarse. Inhomogeneous lath martensite is a weak area in the whole ADS cooling and reflux pipeline. Therefore, the study of cavitation corrosion of CLAM steel welded joints in liquid lead-bismuth alloy can be more economical for ADS system and future fusion demonstration reactor. In this paper, the method of manual TIG welding is first used to cut the same batch of CLAM steel as filling material, and then the 5mm thick CLAM steel plate is welded by plate butt welding, and then the liquid metal cavitation corrosion device is designed independently. The cavitation corrosion tests of CLAM steel weld and base metal samples were carried out in liquid LBE at 550 鈩，

本文编号：1619343