本文選題：BWELDY960Q鋼 + 焊接熱模擬　； 參考：《沈陽工業(yè)大學(xué)》2015年博士論文

【摘要】：焊接結(jié)構(gòu)用BWELDY960Q鋼為低合金高強(qiáng)度鋼,具有較高的強(qiáng)度、良好的韌性,可以減輕焊接結(jié)構(gòu)件的自重,節(jié)約材料。這類鋼在工程機(jī)械、礦山、港口、水電等領(lǐng)域得到廣泛的應(yīng)用,采用焊接性較好的低合金高強(qiáng)度鋼可以使焊接結(jié)構(gòu)壁厚減薄、重量減輕,從而減少焊接的工作量,促進(jìn)工程結(jié)構(gòu)向大型化、輕量化和高效能方向發(fā)展。焊接是影響低合金高強(qiáng)度鋼應(yīng)用的關(guān)鍵技術(shù)問題,從一些工程實(shí)際出發(fā),在各種焊接條件下,低合金高強(qiáng)度鋼焊接接頭出現(xiàn)冷裂紋的產(chǎn)生,韌性的惡化和軟化失強(qiáng)等問題。此外,苛刻的使用條件要求低合金高強(qiáng)度鋼焊接接頭性能不斷提高。低合金高強(qiáng)鋼焊接所面臨要解決的問題是在保證滿足高強(qiáng)度要求的同時(shí),提高焊縫金屬和焊接熱影響區(qū)的韌性及防止裂紋的產(chǎn)生。本文采用焊接熱模擬技術(shù)研究BWELDY960Q鋼在經(jīng)歷單次熱循環(huán)和二次熱循環(huán)后熱影響區(qū)的組織與性能的變化規(guī)律,找到熱影響區(qū)的薄弱區(qū)域。采用常規(guī)MAG焊接方法焊接BWELDY960Q鋼,研究焊接接頭的組織與性能,確定最佳的焊接規(guī)范參數(shù),并將熱模擬與實(shí)際焊接熱影響區(qū)的組織與性能進(jìn)行對比分析。同時(shí)在常規(guī)焊接方法的基礎(chǔ)上施加機(jī)械振動(dòng),通過改變振動(dòng)頻率和振動(dòng)幅值,研究振動(dòng)工藝參數(shù)對焊接接頭組織與性能的影響。熱模擬試驗(yàn)結(jié)果表明,模擬BWELDY960Q鋼單次熱循環(huán)熱影響區(qū),峰值溫度Tp1為1320℃和1200℃粗晶區(qū)、800℃不完全重結(jié)晶區(qū),均發(fā)生脆化現(xiàn)象。粗晶區(qū)的韌性損失達(dá)到母材的82.17%,脆化最為嚴(yán)重,為單次熱循環(huán)熱影響區(qū)韌性惡化的區(qū)域。不完全重結(jié)晶區(qū)的韌性損失達(dá)到母材的46.53%,脆化程度僅次于粗晶區(qū)。當(dāng)焊接線能量在10kJ/cm-40kJ/cm范圍內(nèi)變化時(shí),隨著焊接線能量的增加,粗晶區(qū)的韌性降低,焊接線能量達(dá)到30kJ/cm時(shí),粗晶區(qū)的韌性不再繼續(xù)降低。模擬BWELDY960Q鋼二次熱循環(huán)再熱粗晶區(qū),粗晶區(qū)再經(jīng)歷不同峰值溫度的二次熱循環(huán)后,其韌性有不同程度的提高,峰值溫度Tp2為1200℃未轉(zhuǎn)變再熱粗晶區(qū)和800℃臨界再熱粗晶區(qū)的韌性損失分別達(dá)到母材的73.26%和67.32%,脆化現(xiàn)象較嚴(yán)重,為再熱粗晶區(qū)韌性惡化的區(qū)域,并且兩區(qū)存在“組織遺傳”現(xiàn)象。焊接試驗(yàn)結(jié)果表明,采用常規(guī)MAG焊接方法,焊接電流在180-240A范圍內(nèi)變化,當(dāng)焊接電流為220A時(shí),焊接接頭的力學(xué)性能最佳。此時(shí),焊接接頭的抗拉強(qiáng)度為872MPa,斷面收縮率為41%,延伸率為12.5%,焊縫的沖擊功為60J(-20℃),熔合區(qū)的沖擊功為34J(-20℃)。在振動(dòng)焊接條件下,當(dāng)焊接電流、振動(dòng)頻率和振動(dòng)幅值三個(gè)參數(shù)均發(fā)生變化時(shí),采用正交試驗(yàn)獲得最優(yōu)的振動(dòng)焊接工藝參數(shù),即焊接電流為220A,振動(dòng)幅值為0.05mm,振動(dòng)頻率為40Hz時(shí),BWELDY960Q鋼焊接接頭的焊接接頭的抗拉強(qiáng)度為883MPa,焊縫沖擊功為64J(-20℃),其力學(xué)性能達(dá)到最佳。焊接電流為220A時(shí),BWELDY960Q鋼焊接接頭的力學(xué)性能隨振動(dòng)參數(shù)的變化而變化。隨著振動(dòng)頻率和振動(dòng)幅值的增大,焊接接頭的力學(xué)性能呈現(xiàn)出先提高后降低的趨勢,在不同的振動(dòng)頻率與振動(dòng)幅值條件下焊接接頭的抗拉強(qiáng)度位于790-883MP之間,延伸率位于9-14%之間,焊縫的沖擊功位于50-64J之間。此外,焊接過程中施加機(jī)械振動(dòng)可以改善焊縫的低溫沖擊韌性,常規(guī)焊接時(shí)焊縫的韌脆轉(zhuǎn)變溫度為-73.70℃,施加振動(dòng)焊接后焊縫的韌脆轉(zhuǎn)變溫度為-75.02℃。通過熱模擬與實(shí)際焊接熱影響區(qū)組織與性能的對比分析,熱模擬熱影響區(qū)的奧氏體晶粒比實(shí)際焊接相應(yīng)區(qū)域的晶粒要大很多,熱模擬粗晶區(qū)、細(xì)晶區(qū)的硬度值有所降低,不完全重結(jié)晶區(qū)的硬度值會(huì)略有提高,雖然熱模擬和實(shí)際焊接熱影響區(qū)組織與性能會(huì)有所差別,但利用焊接熱模擬技術(shù)可以揭示熱影響區(qū)組織與性能的變化規(guī)律。
[Abstract]:BWELDY960Q steel is a low alloy and high strength steel for welding structure. It has high strength and good toughness. It can reduce the weight of welding structure and save material. This kind of steel is widely used in the fields of engineering machinery, mine, port, hydropower and so on. The use of low alloy and high strength steel with good weldability can reduce the thickness of welding structure and weight. Reducing the amount of quantity, thus reducing the workload of welding, promoting the engineering structure to be large, lightweight and efficient, welding is the key technical problem that affects the application of low alloy and high strength steel. From some engineering practice, under various welding conditions, the cold crack appears, the toughness is deteriorated and the toughness is deteriorated in various welding conditions. In addition, the hard use conditions require the performance of low alloy high strength steel welded joint to be improved continuously. The problem facing low alloy high strength steel welding is to improve the toughness of weld metal and welding heat affected zone and prevent crack. This paper uses welding hot die. The proposed technique studies the change of microstructure and properties of BWELDY960Q steel in the heat affected zone after a single thermal cycle and two heat cycles. The weak region of the heat affected zone is found. The conventional MAG welding method is used to weld the BWELDY960Q steel. The microstructure and properties of the welded joint are studied, the optimum welding parameters are determined, and the thermal simulation and actual welding are used. The structure and performance of the heat affected zone are compared and analyzed. At the same time, the mechanical vibration is applied on the basis of the conventional welding method. By changing the vibration frequency and vibration amplitude, the influence of the vibration process parameters on the microstructure and properties of the welded joint is studied. The results of the thermal simulation test show that the peak temperature is simulated in the single thermal cycle of BWELDY960Q steel. The degree Tp1 is 1320 C and 1200 C coarse-grained region, and the incompletely recrystallized zone at 800 C is embrittlement. The toughness loss of the coarse-grained region is 82.17% and the embrittlement is the most serious. It is the area where the toughness of the single thermal cycle heat affected zone is deteriorated. The toughness loss of the incomplete recrystallization area is 46.53% of the parent material, and the degree of embrittlement is second only to the coarse-grained zone. When the energy of connection is changed in the range of 10kJ/cm-40kJ/cm, with the increase of the energy of the welding line, the toughness of the coarse-grained region is reduced, and the toughness of the coarse-grained region is no longer reduced when the welding line energy reaches 30kJ/cm. The two heat cycle reheat roughing region of the BWELDY960Q steel is simulated, and the coarse grain region has undergone two thermal cycles without the same peak temperature. With the increase of the same degree, the ductile loss of the unconverted reheat coarse grain region at the peak temperature of Tp2 and the critical reheat roughing zone at 800 degrees centigrade is 73.26% and 67.32% respectively, and the embrittlement phenomenon is serious, which is the area of the toughness deterioration of the reheat coarse grain region, and the "tissue heredity" phenomenon exists in the two zone. The welding test results show that the conventional MAG welding is used. The welding current is changed in the range of 180-240A. When the welding current is 220A, the mechanical performance of the welded joint is the best. At this time, the tensile strength of the welded joint is 872MPa, the section shrinkage is 41%, the elongation is 12.5%, the impact work of the weld is 60J (-20 C), the impact work of the fusion zone is 34J (-20 C). When the three parameters of the flow, the vibration frequency and the amplitude of the vibration are all changed, the optimum vibration welding parameters are obtained by orthogonal test, that is, the welding current is 220A, the vibration amplitude is 0.05mm and the vibration frequency is 40Hz, the tensile strength of the welded joint of the BWELDY960Q steel is 883MPa, the weld impact work is 64J (-20), and the mechanical properties of the welding joint. When the welding current is 220A, the mechanical properties of the welded joint of BWELDY960Q steel vary with the change of the vibration parameters. With the increase of vibration frequency and vibration amplitude, the mechanical properties of the welded joint show a tendency to increase first and then decrease, and the tensile strength of the welded joint under the conditions of different vibration frequency and vibration amplitude is 7. Between 90-883MP, the extension rate is between 9-14%, the impact work of the weld is between 50-64J. In addition, the mechanical vibration of the welding process can improve the low temperature impact toughness of the weld. The toughness and brittleness transition temperature of the weld is -73.70 C during conventional welding, and the toughness and brittleness transition temperature of the weld is -75.02. Compared with the microstructure and properties of the heat affected zone, the austenite grain in the thermal simulated heat affected zone is much larger than that in the actual welding area. The hardness value of the thermal simulated coarse grain region and the fine crystal region will be reduced, the hardness of the incomplete recrystallization zone will be improved slightly, although the microstructure and properties of the thermal simulation and the actual welding heat affected areas will be organized and properties. There are some differences, but the welding thermal simulation technology can reveal the change rule of microstructure and properties in the heat affected zone.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG457.11

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