CLAM钢TIG焊焊缝微观组织及其在550℃静态铅铋中腐蚀行为的研究

发布时间：2018-03-28 02:08

本文选题：CLAM钢　切入点：TIG　出处：《江苏大学》2016年硕士论文

【摘要】：CLAM钢是聚变堆候选材料之一,主要是因为其具备优良的高温力学性能及高温蠕变性能。聚变堆结构复杂,焊接是聚变堆建造过程中必不可少工艺之一,能否解决CLAM钢焊接问题是其能否运用于聚变堆的关键,因此研究CLAM钢焊接性能具有重要意义。CLAM钢作为第一壁候选材料,在工作过程中要与液态金属冷却剂接触,液态LBE是聚变堆冷却剂候选材料,因此研究CLAM钢焊缝在液态LBE中的腐蚀行为也十分必要。通过制备不同W含量的焊丝做为填充材料对CLAM钢进行焊接,焊丝成分在母材的基础上改变焊丝中W的含量,其中W的含量分别为1.5%,3.0%,4.5%。采用不同W含量的焊丝对5mm厚CLAM钢TIG焊时,在试验设计成分范围内,当W含量增加时,WC析出量增加。当加入的W为3.0%时,焊缝的板条组织最为细小,抗拉强度最大,平均抗拉强度达到671.6Mpa,焊接接头拉伸断口有少量韧窝,表现为整体脆性断裂局部韧性断裂。当W含量为4.5㳠时,焊缝的硬度最大。焊缝中存在M23C6型碳化物存在,M的主要元素为Cr、Fe、W、Mn。对比未焊后热处理及焊后760℃/1h热处理发现,未焊后热处理的焊缝冲击吸收功仅为10J,焊后热处理的焊缝冲击吸收功110J,焊后热处理会大大增加焊缝的冲击吸收功,显著提高焊缝的冲击韧性。采用不同的热输入对3mmCLAM钢进行焊接,焊接热输入为1.32KJ·mm-1时,δ铁素体的含量为1.6%,焊接热输入为2.31KJ·mm-1时,δ铁素体的含量为3.5%,随着焊接热输入的增加δ铁素体的含量也随之增加。V含量对CLAM钢焊缝中δ铁素体含量有显著影响,随着V含量的增加,焊缝中δ铁素体含量会随之增加。焊接热输入为2.31KJ·mm-1时,填充材料中V含量从0.20%增加至0.50%时,焊缝中δ铁素体含量由3.5%增加至5.7%。δ铁素体大都分布在原奥氏体晶粒的位置,降低CLAM钢焊缝的冲击韧性。为控制焊缝中δ铁素体的含量,填充材料中V的含量不应过高,同时尽量采用小的焊接热输入进行焊接。本文对CLAM钢焊接接头进行550℃液态LBE合金500h和1000h腐蚀试验发现,经过500h和1000h腐蚀后,失重分别为为0.532 mg·cm-2、0.7872 mg·cm-2;腐蚀速率分别为1.0638mg·m-2·h-1、0.7872 mg·m-2·h-1,平均腐蚀深度分别为0.64μm、1.0067μm,焊缝腐蚀速度随时间下降。焊缝经过腐蚀后,焊缝表面形成双氧化层。外氧化层为Fe3O4,该氧化层质地疏松,且存在较多的小孔,内氧化层为致密的FeCr2O4。氧化膜对基体具有一定的保护性且内氧化层对基体保护性能更好。
[Abstract]:CLAM steel is one of the candidate materials for fusion reactor, mainly because of its high temperature mechanical properties and high temperature creep properties. The fusion reactor complex structure, welding process is essential in the process of the construction of a fusion reactor, can solve the problem of CLAM steel welding is the key to whether the use of fusion reactor, so the study of CLAM steel welding performance is important the significance of.CLAM steel as the first wall material, should be in contact with the liquid metal coolant in the working process, the liquid coolant is LBE fusion reactor, so the study of corrosion behavior of CLAM steel weld in liquid LBE is also very necessary. The preparation of different W content through the wire as filler material for CLAM steel welding. Change the content of the wire wire composition based on W base material, in which the content of W were 1.5%, 3%, 4.5%. with different W content of 5mm thick CLAM steel wire TIG welding, the test The experimental design composition range, when the W content increases, the amount of WC precipitation increased. When the addition of W is 3%, the fine lath microstructure of weld, the maximum tensile strength, average tensile strength reaches 671.6Mpa, the welding joint tensile fracture with small dimple, the performance of the overall local brittle fracture toughness. When the content of W 4.5?, the hardness of the weld. The maximum M23C6 type carbide weld, the main element of M is Cr, Fe, W, found that /1h 760 degrees of heat treatment and welding Mn. compare after welding, weld seam impact without postweld heat treatment of the absorbed energy is only 10J, the impact of weld after welding the absorbed energy of 110J heat treatment, heat treatment after welding can greatly increase the impact toughness of the weld, significantly improve the impact toughness of the weld heat input. The different of 3mmCLAM steel welding, welding heat input is 1.32KJ - mm-1, delta ferrite content was 1.6%, the heat input was 2.31K J mm-1, delta ferrite content is 3.5%, with the increase of the welding heat input of delta ferrite content also increased the content of.V had significant effects on the CLAM steel weld ferrite content, with the increase of V content in the weld ferrite content increases with the welding heat. The input is 2.31KJ - mm-1, with V content in the material increased from 0.20% to 0.50%, the weld ferrite content increased from 3.5% to 5.7%. are mostly distributed in the ferrite austenite grain position, reduce the impact toughness of CLAM steel weld. For control of weld in the delta ferrite content, content in the filling material of V should not be too high, while minimizing the use of small welding heat input welding. The welded joints of CLAM steel for 550 DEG C liquid LBE alloy 500h and 1000h corrosion test showed that after 500h and 1000h after corrosion weightlessness were 0.532 Mg - cm-2,0.7872 Mg - cm-2; corrosion rate Rates were 1.0638mg - m-2 - h-1,0.7872 Mg - m-2 - H-1, the average corrosion depth was 0.64 m, 1.0067 m, the weld corrosion rate decreased with time. The weld after corrosion, weld surface forming a double oxide layer. The external oxidation layer is Fe3O4, the oxide layer of loose texture, and there are more holes FeCr2O4., the internal oxidation layer of dense oxide film to the substrate has a certain protective oxide layer on the substrate and better protection performance.

【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG457.11

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