本文選題：Fe基非晶合金 + 藥芯焊絲��； 參考：《中國(guó)石油大學(xué)(華東)》2015年碩士論文

【摘要】：Fe基非晶態(tài)合金具有獨(dú)特的結(jié)構(gòu)和優(yōu)異的力學(xué)性能及耐腐蝕性能,其作為焊絲具有成分均勻、浸潤(rùn)性強(qiáng)等特點(diǎn),是一種極具發(fā)展?jié)摿Φ暮附有虏牧?具有廣闊的應(yīng)用前景。X80管線鋼服役條件艱苦,對(duì)焊接接頭的強(qiáng)度和耐腐蝕性能提出了更高的要求。利用TIG焊對(duì)X80鋼進(jìn)行非晶焊接,可充分利用非晶合金的優(yōu)異性能,有效提高焊接接頭強(qiáng)度和耐腐蝕性能。本文采用鐵基非晶合金藥芯焊絲,結(jié)合TIG焊技術(shù)對(duì)X80管線鋼薄板進(jìn)行了對(duì)接焊接,利用光學(xué)顯微鏡、X射線衍射儀、掃描電子顯微鏡、能譜儀、顯微硬度計(jì)、電子萬(wàn)能試驗(yàn)機(jī)和電化學(xué)測(cè)試系統(tǒng)等設(shè)備分析了非晶焊接接頭的組織結(jié)構(gòu)、物相組成、力學(xué)性能和耐腐蝕性等性能。同時(shí)研究了熔合比、功率密度工藝參數(shù)和焊后熱處理工藝對(duì)焊接接頭組織結(jié)構(gòu)和性能的影響規(guī)律,并探討了焊接接頭的斷裂機(jī)制和腐蝕機(jī)理。研究結(jié)果表明,X80管線鋼的非晶焊接接頭是由(Fe,Cr)固溶體、Mn4B相及非晶等組成的復(fù)合組織。熔合區(qū)域?yàn)橐粭l狹窄的平面晶,寬度約為10μm,焊縫由胞狀樹枝晶、灰色細(xì)條狀組織、灰黑色長(zhǎng)條狀組織和白色細(xì)條狀組織組成。當(dāng)熔合比增大至0.68時(shí),焊縫轉(zhuǎn)變?yōu)榛疑w上分布著細(xì)小樹枝晶的組織。隨著功率密度的增加,焊縫區(qū)域的晶粒尺寸增大,硬度降低。焊接接頭經(jīng)熱處理后,非晶結(jié)構(gòu)發(fā)生了晶化,組織實(shí)現(xiàn)均勻化。TIG焊焊接接頭焊縫區(qū)域的平均硬度為776.9Hv0.2。焊接接頭具有拉伸正斷的脆性行為和較低的沖擊韌性。焊接接頭抗拉強(qiáng)度為551MPa,延伸率為0.40%,沖擊韌性為2.5J?cm-2,斷口為準(zhǔn)解理斷裂和典型的非晶剪切帶斷裂混合類型。經(jīng)熱處理后,焊縫區(qū)域的顯微硬度明顯下降,焊接接頭的拉伸強(qiáng)度變化不大,延伸率和沖擊韌性增大。經(jīng)過(guò)900℃熱處理后,焊縫平均硬度約為417.5Hv0.2,比熱處理前降低46.3%,焊接接頭的抗拉強(qiáng)度為398.5MPa,延伸率為5.22%,沖擊韌性為15J?cm-2,斷口類型為低塑性的韌性斷裂,相比于熱處理前焊接接頭的塑韌性得到明顯的改善。非晶焊接接頭焊縫區(qū)域自腐蝕電位為-344.8mV,自腐蝕電流密度為9.61μA/cm2,耐蝕性能較母材有較大的提高。擬合等效電路為R(Q(R(QR))),電極系統(tǒng)包括“總電極金屬/溶液”界面和蝕孔內(nèi)“溶液/金屬”界面,鈍化膜不夠致密,有發(fā)生點(diǎn)蝕傾向。經(jīng)過(guò)900℃熱處理后,自腐蝕電位為-375.1mV,自腐蝕電流密度為10.30μA/cm2,擬合等效電路為R(QR),電極系統(tǒng)為“總電極金屬/溶液”界面,表現(xiàn)為致密的鈍化膜。
[Abstract]:Fe-based amorphous alloy has unique structure, excellent mechanical properties and corrosion resistance. As a welding wire, it has the characteristics of uniform composition and strong wettability, so it is a new welding material with great development potential. The service conditions of X80 pipeline steel have a broad application prospect. The strength and corrosion resistance of welded joints are required higher. The amorphous welding of X80 steel by TIG welding can make full use of the excellent properties of the amorphous alloy and effectively improve the strength and corrosion resistance of the welded joint. In this paper, the iron-based amorphous alloy flux-cored wire and TIG welding technology are used to weld the X80 pipeline steel sheet. The X ray diffractometer, scanning electron microscope, energy spectrometer, microhardness meter are used in the welding of X80 pipeline steel sheet. The microstructure, phase composition, mechanical properties and corrosion resistance of amorphous welded joints were analyzed by electronic universal testing machine and electrochemical testing system. At the same time, the influence of fusion ratio, power density process parameters and post-weld heat treatment process on the microstructure and properties of welded joints were studied. The fracture mechanism and corrosion mechanism of welded joints were also discussed. The results show that the amorphous welded joints of X80 pipeline steel are composed of (FetoCr) solid solution and amorphous phase. The fusion zone is a narrow planar crystal with a width of about 10 渭 m. The weld is composed of cellular dendrite, gray fine stripe, gray black long stripe and white fine stripe. When the fusion ratio is increased to 0.68, the weld is transformed into a structure with fine dendrites distributed on the gray matrix. With the increase of power density, the grain size of weld increases and the hardness decreases. After heat treatment, the amorphous structure was crystallized, and the average hardness of weld zone of TIG welded joint was 776.9 Hv0.2. The welded joint has tensile brittle behavior and low impact toughness. The tensile strength of the welded joint is 551 MPA, the elongation is 0.40, the impact toughness is 2.5 J / cm ~ (-2), the fracture surface is quasi-cleavage fracture and the typical mixed type of amorphous shear band fracture. After heat treatment, the microhardness of weld zone decreased obviously, the tensile strength of welded joint changed little, and the elongation and impact toughness increased. After heat treatment at 900 鈩，

本文編號(hào)：2056025