本文選題：雙相不銹鋼　切入點：焊接　出處：《蘭州理工大學(xué)》2017年碩士論文

【摘要】：雙相不銹鋼發(fā)展至今,因其具有良好的抗氧化性、力學(xué)性能及耐腐蝕性能,越來越多的應(yīng)用到油田平臺、遠洋航海、化工工業(yè)等領(lǐng)域。特別是在化工工業(yè)領(lǐng)域,良好的耐氯化物腐蝕性能使雙相不銹鋼不僅在酸類、聚合物等產(chǎn)品中得到使用,更被廣泛的應(yīng)用到了壓力容器、反應(yīng)器、熱交換器等設(shè)備之中。SAF2205雙相不銹鋼作為最常用的雙相不銹鋼,因其具有良好的耐腐蝕性能以及焊接性能,常采用氣體保護鎢極氬弧焊(GTAW)、手工電弧焊(SMAW)以及埋弧自動焊(SAW)等方法進行焊接。但在焊接過程中,因為焊接熱循環(huán)的存在,導(dǎo)致了析出相以及焊接應(yīng)力的產(chǎn)生,影響了焊接接頭的性能。為此,研究不同焊接方法及熱處理工藝對SAF2205雙相不銹鋼焊接接頭各項性能的影響,對于其在實際生產(chǎn)中的應(yīng)用具有一定的理論和實際意義。本文采用GTAW和SMAW兩種不同的焊接方法,前期通過對比兩種焊接方法對SAF2205雙相不銹鋼各項性能影響的優(yōu)劣,分析不同焊接方法對焊接接頭的力學(xué)性能及耐腐蝕性能的影響;后期對焊接試件進行退火熱處理,通過對比不同退火溫度及保溫時間后焊接接頭力學(xué)性能及耐腐蝕性能,研究了熱處理對兩種不同焊接方法焊接接頭的應(yīng)力消除效果、力學(xué)性能的改變及對耐腐蝕性能的影響,得到如下幾條主要結(jié)論:(1)GTAW和SMAW兩種焊接方法對試樣焊縫區(qū)抗拉強度及抗彎強度的影響不大,且均高于母材。但焊縫區(qū)的沖擊韌性均低于母材,且SMAW明顯低于GTAW。金相試驗表明,焊縫區(qū)晶粒粗大是引起其沖擊韌性降低的主要原因。(2)GTAW和SMAW兩種焊接方法焊縫區(qū)有著比母材更優(yōu)良的耐腐蝕性能。這是因為焊縫區(qū)具有良好的相比例。(3)試樣經(jīng)熱處理后的試驗結(jié)果表明,在規(guī)定的退火溫度及保溫時間內(nèi),拉伸強度和抗彎強度均沒有明顯的變化;沖擊試驗結(jié)果表明,過高的熱處理溫度使焊縫及熱影響區(qū)的沖擊吸收功降低。因此,退火溫度不宜超過350℃。(4)焊接試樣熱處理后的耐腐蝕試驗表明,試樣的腐蝕速率隨退火溫度的提高以及保溫時間的延長而增加;在較低的280℃退火時,保溫時間對試樣的腐蝕速率影響不大。(5)焊接所產(chǎn)生的應(yīng)力主要集中在焊縫熱影響區(qū)。在280℃去應(yīng)力退火,焊接應(yīng)力隨保溫時間的延長而下降。試驗表明,保溫6h焊接應(yīng)力下降7.7%,保溫12h焊接應(yīng)力下降14.5%。
[Abstract]:Dual-phase stainless steel has been widely used in oil platform, ocean navigation, chemical industry and so on because of its good oxidation resistance, mechanical properties and corrosion resistance.Especially in the field of chemical industry, because of its good corrosion resistance to chloride, duplex stainless steel is not only used in acid, polymer and other products, but also widely used in pressure vessels and reactors.As the most commonly used duplex stainless steel, the. SAF2205 duplex stainless steel has good corrosion resistance and welding performance.Gas shielded argon tungsten arc welding (GTAW), manual arc welding (SMAW) and submerged arc welding (SAW) are often used for welding.However, in the welding process, due to the existence of welding thermal cycle, the precipitate phase and the welding stress are produced, which affects the performance of the welded joint.Therefore, it is of theoretical and practical significance to study the effects of different welding methods and heat treatment processes on the properties of SAF2205 duplex stainless steel welded joints.In this paper, two different welding methods, GTAW and SMAW, are used to analyze the effects of different welding methods on the mechanical properties and corrosion resistance of the welded joints by comparing the advantages and disadvantages of the two welding methods on the properties of SAF2205 duplex stainless steel.The stress relief effect of heat treatment on two different welding methods was studied by comparing the mechanical properties and corrosion resistance of welded joints after different annealing temperatures and holding time.With the change of mechanical properties and the effect on corrosion resistance, the main conclusions are as follows: (1) GTAW and SMAW welding methods have little effect on tensile strength and bending strength of weld zone, and both of them are higher than base metal.However, the impact toughness of weld zone is lower than that of base metal, and SMAW is obviously lower than that of GTAW.The results of metallographic test show that the coarse grain size in the weld zone is the main reason for the decrease of impact toughness. The weld zone has better corrosion resistance than the base metal by the two welding methods, I. e., GTAW and SMAW.This is because the weld zone has a good phase ratio. The test results after heat treatment show that the tensile strength and bending strength of the specimen have no obvious change within the specified annealing temperature and holding time, and the impact test results show that,Too high heat treatment temperature reduces the impact absorption energy of weld and heat affected zone.Therefore, the corrosion resistance of the welded specimens after heat treatment should not exceed 350 鈩，

本文編號：1729018