316L鋼焊接接頭在液態(tài)鉛鉍合金中的空泡腐蝕行為研究
發(fā)布時間：2018-08-09 07:57
【摘要】：鉛鉍共晶合金(LBE)具有熔點低,載熱能力強,中子特性良好等優(yōu)良性能,是加速器次臨界驅(qū)動系統(tǒng)(ADS)的散裂靶和冷卻劑的首要候選材料。但是鉛鉍合金會對暴露于液態(tài)金屬環(huán)境的包層材料造成比較嚴(yán)重的腐蝕。如在核工程冷卻循環(huán)回路中,核主泵葉輪與液態(tài)金屬做高速相對運動時使葉輪上的局部區(qū)域形成壓力突變區(qū),氣體析出后在葉輪表面形成氣泡,大量的氣泡潰滅對金屬表面造成空泡腐蝕,導(dǎo)致部件使用壽命的降低和維修成本的提高。316L鋼具有優(yōu)良的力學(xué)性能和耐腐蝕性能,常用作ADS冷卻循環(huán)回路的包層材料與主泵葉輪材料。在核工程中許多結(jié)構(gòu)都使用熔焊的方法進(jìn)行裝配和制造,而焊縫組織一般存在成分偏析、組織粗大等缺陷,是整個冷卻循環(huán)回路薄弱區(qū)域。因此研究316L鋼焊接接頭在液態(tài)鉛鉍合金中的空泡腐蝕可以為ADS系統(tǒng)及未來聚變示范堆能夠更加經(jīng)濟(jì)、安全地應(yīng)用提供理論基礎(chǔ)。本文針對316L不銹鋼,分別采用316L鋼母材和鈷基合金作為填充金屬進(jìn)行TIG焊,并進(jìn)行焊后熱處理。自主設(shè)計和研發(fā)液態(tài)金屬超聲空蝕設(shè)備,在550℃液態(tài)PbBi中進(jìn)行316L母材、熱處理前后316L焊縫、熱處理前后鈷基合金焊縫的空泡腐蝕試驗。利用SEM與AFM表征不同時間空蝕后各組試樣的表面形貌,并研究表面形貌隨空蝕時間的變化規(guī)律和分析各組試樣的空泡腐蝕行為;測量各組試樣不同時間空蝕后表面粗糙度與腐蝕坑深度的變化以研究耐空蝕性差異,進(jìn)而研究不同填充材料和熱處理工藝參數(shù)對焊縫液態(tài)LBE中空泡腐蝕的影響;另外,通過對比靜態(tài)腐蝕和空泡腐蝕100h后焊縫截面氧化層形貌以及元素的變化,探索熔焊接頭表面在液態(tài)LBE中產(chǎn)生的溶解與氧化腐蝕和空泡腐蝕的聯(lián)合作用機(jī)制。試驗結(jié)果表明,316L焊縫與母材試樣表面粗糙度和最大腐蝕坑深度隨著空蝕試驗時間的延長而不斷增加,母材表現(xiàn)出的耐空蝕性大大優(yōu)于焊縫,耐空蝕性差異主要與兩者的金相組織有關(guān)。將316L鋼焊縫進(jìn)行固溶處理后其耐空蝕性得到改善,但依然沒有316L母材耐空蝕性好。另外,通過對比316L鋼焊縫靜態(tài)腐蝕100h和空泡腐蝕100h后焊縫截面的元素變化發(fā)現(xiàn),液態(tài)鉛鉍合金中的溶解與氧化腐蝕和空泡腐蝕會相互促進(jìn),它們的聯(lián)合作用對焊縫造成更加嚴(yán)重的破壞。鈷基合金耐腐蝕性很好,因此本文利用鈷基合金作為填充材料對316L鋼進(jìn)行TIG對接焊,并將鈷基合金焊縫進(jìn)行不同溫度的焊后熱處理,之后進(jìn)行液態(tài)鉛鉍中不同時間的空泡腐蝕試驗。試驗結(jié)果表明鈷基合金焊縫的耐空蝕性優(yōu)于316L鋼焊縫,且不同溫度焊后熱處理后,鈷基合金焊縫的耐空蝕性都得到改善,其中750℃熱處理后鈷基合金焊縫耐空蝕性最優(yōu),其次為700℃熱處理,800℃熱處理后鈷基合金耐空蝕性最差。本文所有試樣在空蝕試驗過程中,316L母材、固溶處理前后316L鋼焊縫、未熱處理鈷基合金焊縫四組試樣在空蝕過程中都發(fā)生了不同程度的加工硬化,其中316L母材的加工硬化程度最高,鈷基合金焊縫加工硬化程度最低;三組溫度熱處理后的鈷基合金焊縫幾乎沒有發(fā)生加工硬化,加工硬化程度在空蝕20h內(nèi)略微增加,且在20h后表面硬度略微下降。經(jīng)過綜合分析,在本文研究的所有材料中,母材的耐空蝕性能最優(yōu),其次是750℃熱處理后的鈷基合金焊縫,再是固溶處理后的316L焊縫。
[Abstract]:Lead bismuth eutectic alloy (LBE) has good properties such as low melting point, strong heat carrying capacity and good neutron characteristics. It is the primary candidate for the spallation target and coolant of the accelerator subcritical drive system (ADS). But lead bismuth alloy will cause serious corrosion to the cladding material exposed to the liquid metal environment. For example, in the cooling cycle of nuclear engineering. In the road, when the impeller of the nuclear main pump and the liquid metal are moving relative to the liquid metal, the local area on the impeller is formed, the gas bubbles are formed on the surface of the impeller, and a large number of bubbles collapse on the metal surface, resulting in cavitation corrosion on the metal surface, which leads to the improvement of the service life of the components and the improvement of the maintenance cost of the.316L steel with excellent mechanical properties. The cladding material and the main pump impeller are commonly used as the ADS cooling loop. Many structures in the nuclear engineering are assembled and manufactured by the fusion welding method. The weld organization usually has the defects such as composition segregation and coarse organization, which is the weak area of the whole cooling loop. Therefore, the study of 316L steel welded joint is studied. The cavitation corrosion in liquid lead bismuth alloy can provide a theoretical basis for the more economical and safe application of ADS system and future fusion demonstration reactor. In this paper, the TIG welding of 316L stainless steel with 316L steel and cobalt base alloy is used respectively as filled metal, and the post weld heat is carried out. The ultrasonic cavitation of liquid metal is designed and developed independently. The equipment, the 316L parent material, 316L weld before and after heat treatment at 550 C, and the cavitation corrosion test of the cobalt base alloy weld before and after heat treatment. Using SEM and AFM to characterize the surface morphology of each sample after different time cavitation, and study the change rules of surface morphology with the cavitation time and the analysis of the cavitation corrosion behavior of each sample. The changes of surface roughness and corrosion pit depth after different time cavitation were studied to study the difference of cavitation resistance. Then the effects of different filling materials and heat treatment parameters on the corrosion of liquid LBE hollow bubble were studied. In addition, the morphology of the oxidation layer of the weld section and the change of elements after 100h were compared with static corrosion and cavitation corrosion. The joint action mechanism of the dissolving and oxidation corrosion and cavitation corrosion in the liquid LBE is explored. The results show that the surface roughness and the maximum corrosion pit depth of the 316L weld and the parent material increase with the time of cavitation test, and the cavitation resistance of the parent material is much better than that of the weld. The corrosion resistance is mainly related to the metallographic structure of the two. The cavitation resistance of 316L steel welds is improved after solid solution treatment, but still there is no good cavitation resistance of 316L parent material. In addition, the dissolution and oxidation of the liquid lead bismuth alloy is found by the comparison of the element modification of the weld cross section after the static corrosion of the 316L steel weld 100h and the cavitation corrosion 100h. Corrosion and cavitation corrosion will promote each other, their joint effects cause more serious damage to the weld. The corrosion resistance of cobalt base alloys is very good. Therefore, the cobalt base alloy is used as filling material for TIG butt welding of 316L steel, and the cobalt base alloy welds are heat treated at different temperatures after welding, and then the liquid lead bismuth is different. The test results show that the cavitation resistance of the cobalt base alloy welds is better than that of 316L steel, and the cavitation resistance of the cobalt base alloy welds is improved after heat treatment at different temperatures. The corrosion resistance of the cobalt base alloy welds at 750 C is the best, the heat treatment is 700 degrees C, and the cobalt base alloy after heat treatment at 800. In the process of cavitation test, all specimens of this paper in the cavitation test, 316L material, 316L steel weld before and after solution treatment, four groups of cobalt base alloy welds without heat treatment, have different degree of hardening during the cavitation process, of which the working hardening of 316L is the highest, the working hardening of cobalt base alloy welds is the lowest; three groups. The weld seam of cobalt base alloy after temperature and heat treatment has hardly been hardened, and the degree of working hardening is slightly increased in cavitation 20h, and the hardness of the surface decreases slightly after 20h. After comprehensive analysis, the corrosion resistance of the parent material is the best in all the materials studied in this paper, followed by the weld of cobalt base alloy after heat treatment at 750 C, and then solid solution. 316L weld after treatment.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG407;TG441.8
本文編號：2173427
[Abstract]:Lead bismuth eutectic alloy (LBE) has good properties such as low melting point, strong heat carrying capacity and good neutron characteristics. It is the primary candidate for the spallation target and coolant of the accelerator subcritical drive system (ADS). But lead bismuth alloy will cause serious corrosion to the cladding material exposed to the liquid metal environment. For example, in the cooling cycle of nuclear engineering. In the road, when the impeller of the nuclear main pump and the liquid metal are moving relative to the liquid metal, the local area on the impeller is formed, the gas bubbles are formed on the surface of the impeller, and a large number of bubbles collapse on the metal surface, resulting in cavitation corrosion on the metal surface, which leads to the improvement of the service life of the components and the improvement of the maintenance cost of the.316L steel with excellent mechanical properties. The cladding material and the main pump impeller are commonly used as the ADS cooling loop. Many structures in the nuclear engineering are assembled and manufactured by the fusion welding method. The weld organization usually has the defects such as composition segregation and coarse organization, which is the weak area of the whole cooling loop. Therefore, the study of 316L steel welded joint is studied. The cavitation corrosion in liquid lead bismuth alloy can provide a theoretical basis for the more economical and safe application of ADS system and future fusion demonstration reactor. In this paper, the TIG welding of 316L stainless steel with 316L steel and cobalt base alloy is used respectively as filled metal, and the post weld heat is carried out. The ultrasonic cavitation of liquid metal is designed and developed independently. The equipment, the 316L parent material, 316L weld before and after heat treatment at 550 C, and the cavitation corrosion test of the cobalt base alloy weld before and after heat treatment. Using SEM and AFM to characterize the surface morphology of each sample after different time cavitation, and study the change rules of surface morphology with the cavitation time and the analysis of the cavitation corrosion behavior of each sample. The changes of surface roughness and corrosion pit depth after different time cavitation were studied to study the difference of cavitation resistance. Then the effects of different filling materials and heat treatment parameters on the corrosion of liquid LBE hollow bubble were studied. In addition, the morphology of the oxidation layer of the weld section and the change of elements after 100h were compared with static corrosion and cavitation corrosion. The joint action mechanism of the dissolving and oxidation corrosion and cavitation corrosion in the liquid LBE is explored. The results show that the surface roughness and the maximum corrosion pit depth of the 316L weld and the parent material increase with the time of cavitation test, and the cavitation resistance of the parent material is much better than that of the weld. The corrosion resistance is mainly related to the metallographic structure of the two. The cavitation resistance of 316L steel welds is improved after solid solution treatment, but still there is no good cavitation resistance of 316L parent material. In addition, the dissolution and oxidation of the liquid lead bismuth alloy is found by the comparison of the element modification of the weld cross section after the static corrosion of the 316L steel weld 100h and the cavitation corrosion 100h. Corrosion and cavitation corrosion will promote each other, their joint effects cause more serious damage to the weld. The corrosion resistance of cobalt base alloys is very good. Therefore, the cobalt base alloy is used as filling material for TIG butt welding of 316L steel, and the cobalt base alloy welds are heat treated at different temperatures after welding, and then the liquid lead bismuth is different. The test results show that the cavitation resistance of the cobalt base alloy welds is better than that of 316L steel, and the cavitation resistance of the cobalt base alloy welds is improved after heat treatment at different temperatures. The corrosion resistance of the cobalt base alloy welds at 750 C is the best, the heat treatment is 700 degrees C, and the cobalt base alloy after heat treatment at 800. In the process of cavitation test, all specimens of this paper in the cavitation test, 316L material, 316L steel weld before and after solution treatment, four groups of cobalt base alloy welds without heat treatment, have different degree of hardening during the cavitation process, of which the working hardening of 316L is the highest, the working hardening of cobalt base alloy welds is the lowest; three groups. The weld seam of cobalt base alloy after temperature and heat treatment has hardly been hardened, and the degree of working hardening is slightly increased in cavitation 20h, and the hardness of the surface decreases slightly after 20h. After comprehensive analysis, the corrosion resistance of the parent material is the best in all the materials studied in this paper, followed by the weld of cobalt base alloy after heat treatment at 750 C, and then solid solution. 316L weld after treatment.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG407;TG441.8
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