【摘要】：目前我國列車轉(zhuǎn)向架典型材質(zhì)為進口高強耐候鋼S355J2W(H)、SMA490BW,以及國產(chǎn)的Q345系列鋼。由于進口鋼的疲勞性能較好,低溫沖擊性能較優(yōu)越,因此高速列車轉(zhuǎn)向架多依賴進口鋼。在地鐵等軌道交通領域,國產(chǎn)Q345鋼應用較多,但在服役環(huán)境較為苛刻的城市還是多采用進口鋼種,由此看來轉(zhuǎn)向架用鋼的國產(chǎn)化程度不高。在推進轉(zhuǎn)向架鋼國產(chǎn)化的進程中,對國產(chǎn)鋼的焊接性研究十分重要。研究材料的焊接性,通過一定的方法對焊接接頭的組織轉(zhuǎn)變和力學行為進行研究,可以對材料本身的組織、性能等建立基礎數(shù)據(jù)庫,此外,通過對焊材匹配性和焊接工藝的研究,匹配不同的焊接材料、選擇合適的焊接工藝參數(shù),達到提高其焊接接頭性能的目標,從而為國產(chǎn)鋼的應用推廣提供便利。本文通過對Q345C鋼和利用ER50Q、ER80S-G焊接得到的焊接熔敷金屬進行連續(xù)冷卻轉(zhuǎn)變試驗,分析在不同的冷卻速度下材料的組織轉(zhuǎn)變規(guī)律和硬度變化;通過對熱模擬得到的Q345C焊接熱影響區(qū)和實際的焊接接頭進行組織轉(zhuǎn)變分析和力學性能測試,得到以下結(jié)論:Q345C的SHCCT曲線可以分為四個區(qū),按照溫度從高到低轉(zhuǎn)變順序依次為鐵素體、珠光體、貝氏體和馬氏體。其中貝氏體區(qū)轉(zhuǎn)變范圍較寬,從冷卻速度0.2℃/s～100℃/s可在微觀組織中分別看到上貝氏體、粒狀貝氏體和竹葉狀的下貝氏體;應用彩色金相技術(shù),可以觀察到由于不同位向而呈不同顏色的塊狀多邊形鐵素體組織,在金相顯微鏡下即可觀察到上貝氏體鐵素體板條間的殘余奧氏體;另外,在區(qū)分貝氏體和馬氏體時,應用彩色金相技術(shù),可以清晰的觀察到呈竹葉狀的下貝氏體和在較高的冷卻速度下呈板條狀規(guī)則排列的低碳馬氏體,成功地達到辨認組織并對組織進行定量分析的目的;SHCCT曲線的準確性較好,也適用于激光-MAG復合焊等新型工藝方法;兩種熔敷金屬的SWCCT曲線可分為三個區(qū),分別為鐵素體、珠光體和貝氏體區(qū),貝氏體轉(zhuǎn)變范圍較寬,包含針狀鐵素體、粒狀貝氏體、板條貝氏體以及無碳貝氏體等,ER80S-G熔敷金屬中針狀鐵素體在較低冷速和較高的溫度區(qū)間開始產(chǎn)生,含量高于ER50Q熔敷金屬;Q345C焊接接頭中ER50Q焊縫和ER80S-G焊縫的第一道和第二道焊縫由塊狀鐵素體、針狀鐵素體、珠光體組成,第三道和第四道焊縫由沿晶界析出的條狀先共析鐵素體、晶內(nèi)的針狀鐵素體、貝氏體和少量的珠光體組成,ER80S-G焊縫中的先共析鐵素體較少,針狀鐵素體較多;ER80S-G焊縫的硬度、抗拉強度和屈服強度均高于ER50Q焊縫,兩者均高于母材;ER80S-G焊縫和ER50Q焊縫的FATT50分別為-5.6℃和-1.1℃,ER80S-G焊縫的韌脆轉(zhuǎn)變溫度較低;可選擇ER80S-G焊絲來提高焊縫的強度和韌性;采用準確性較好的烏威經(jīng)驗公式可實現(xiàn)焊接工藝參數(shù)與t8/5之間的換算;應用第四道焊接工藝參數(shù)計算ER50Q和ER80S-G第四道焊縫的t8/5,通過對ER50Q焊縫和ER80S-G焊縫的第四道焊縫的組織觀察和硬度對比,與SWCCT曲線中相同t8/5下的組織硬度相當,進一步驗證了試驗測得的SWCCT曲線是準確的。
[Abstract]:At present, the typical material of China's train bogie is imported high-strength weather-resistant steel S355JW (H), SMA490BW, and domestic Q345 series steel. Because the fatigue property of imported steel is good, the low-temperature impact performance is superior, so the high-speed train bogie depends on imported steel. In the field of rail transit such as subway, domestic Q345 steel has more applications, but in more demanding cities or more imported steel grades in the service environment, it appears that the degree of localization of steel used for bogie is not high. It is very important to study the weldability of domestic steel in the process of propelling bogie steel. The welding property of the material is studied, the microstructure and mechanical behavior of the welding joint are studied by a certain method, and the basic database can be established for the structure and the property of the material itself. In addition, the welding materials are matched by the research of the matching property and the welding process of the butt welding material, The proper welding process parameters are selected to achieve the aim of improving the welding joint performance, thus facilitating the application and popularization of home-made steel. In this paper, the microstructure transition rule and hardness change of the material under different cooling rates are analyzed by the continuous cooling transformation test of the welding fusion metal obtained by welding Q345C steel and using ER50Q and ER80S-G. The results show that the SHCCT curve of Q345C can be divided into four regions, which is ferrite and pearlite in turn from high to low transition sequence according to the temperature. bainite and martensite. wherein the transformation range of the bainite region is wide, the upper bainite, the granular bainite and the bamboo leaf-like lower bainite can be seen in the microstructure respectively from the cooling speed of 0. 2 DEG C/ s to 100 DEG C/ s, and the color gold phase technology is applied, It can be observed that the residual austenite between upper bainite ferrite strips can be observed under the gold phase microscope due to the mass polygonal ferrite structure with different colors and different colors; in addition, when the bainite and martensite are distinguished, the color gold phase technology is applied, can clearly observe the lower bainite which is in the form of bamboo leaves and the low-carbon martensite which is arranged at a high cooling speed in a strip-shaped rule, so that the purpose of identifying the tissue and quantitatively analyzing the tissue is successfully achieved, the accuracy of the SHCCT curve is good, The SWCCT curve of two welding metals can be divided into three regions, namely ferrite, pearlite and bainite region, bainite transformation range is wide, acicular ferrite, granular bainite, lath bainite and carbon-free bainite are contained, The acicular ferrite in the ER80S-G cladding metal is produced at a lower cold speed and a higher temperature interval, the content is higher than that of the ER50Q fusion coating metal, the first and second welding seams of the ER50Q weld and the ER80S-G weld in the Q345C welding joint consist of massive ferrite, acicular ferrite and pearlite, The third and fourth welds consist of ferrite, acicular ferrite in the crystal, bainite and a small amount of pearlite, which are precipitated along the grain boundaries. The first co-evolution ferrite in the ER80S-G weld is less, the acicular ferrite is much more, the hardness of the ER80S-G weld is higher, The tensile strength and yield strength are higher than that of ER50Q weld, both of which are higher than that of parent material; the FATT50 of ER80S-G weld and ER50Q weld is -5. 6 鈩，

本文編號：2287259