本文選題：30CrMnSi + 焊接冷裂紋��； 參考：《南昌航空大學》2015年碩士論文

【摘要】：某一重要構件使用30CrMnSi鋼生產(chǎn),但是,在焊接的過程中出現(xiàn)了一系列問題。其中大量出現(xiàn)的冷裂紋使得該焊接結構件無法滿足該工廠的缺陷率要求,造成了大量的成本浪費,為此對該焊結構件焊接冷裂紋缺陷的控制顯得十分有必要。針對冷裂紋這一問題,提出了使用紅外照射裝置焊前預熱、焊后緊急后熱以及隨焊后熱的方法,減少淬硬組織,以達到降低冷裂紋敏感性的目的。為了達到與實際生產(chǎn)條件相同的目的,本文使用1.8mm厚的30CrMnSi鋼,采用該結構中占多數(shù)的對接形式。分別采用CO2氣體保護焊(CO2焊)和鎢極氬弧焊(TIG焊)進行試驗,研究了預熱、及時后熱和隨焊后熱對脆硬組織及影響規(guī)律,同時,研究了多次補焊對焊接接頭組織及性能的影響規(guī)律,分析了焊后及時后熱對補焊接頭的作用。研究結果表明:較小的CO2焊有效熱輸入有利于減少淬硬組織、降低淬硬傾向而控制焊接冷裂紋。使用隨焊紅外照射可以降低焊接接頭完全淬火區(qū)組織中脆硬組織片狀馬氏體的含量,當紅外照射裝置與焊槍的距離為250mm時,該區(qū)域的最高顯微硬度為511.1HV,較普通焊接條件降低了164.1HV,其抗拉強度為950MPa達到了母材的91.7%。在該隨焊紅外照射條件下,可以有效地減少了完全淬火區(qū)中的脆硬組織,在一定程度上降低了冷裂紋敏感性。在使用TIG焊的條件下,采用紅外隨焊裝置且距離為50mm到150mm時均能有效的減少淬硬組織的含量,但是當焊槍距離大于150mm時,由于在馬氏體轉變完成后進行了升溫,使得該位置的組織經(jīng)歷了一次“回火”,產(chǎn)生回火脆性,導致冷裂紋敏感性的提高。當預熱溫度為150℃時,完全淬火區(qū)的最高顯微硬度為470HV,較不預熱條件下的560HV有了明顯的降低。當及時后熱時間為6min時,其對降低冷裂紋敏感性的作用最為明顯,隨著后熱時間的增加,由于回火作用更加明顯,冷裂紋敏感性有所增加。使用TIG焊對缺陷進行補焊,對三種不同補焊形式進行了研究,對不同補焊次數(shù)的影響進行了分析。表明隨著補焊次數(shù)的增加,三種不同的補焊形式的焊接接頭抗拉強度均呈現(xiàn)出下降的趨勢,接頭軟化也出現(xiàn)惡化的趨勢。三種補焊方式中,連續(xù)氣孔補焊對接頭的影響最大,焊縫中心氣孔補焊和熔合線補焊對接頭的性能影響較小。補焊后使用及時后熱可以有效的降低完全淬火區(qū)的淬硬組織含量,提高接頭抗冷裂性能。
[Abstract]:An important component is made of 30CrMnSi steel, but a series of problems appear in the welding process. The large number of cold cracks make the welding structure can not meet the requirements of the factory defect rate, resulting in a large amount of cost waste, so it is very necessary to control the welding cold crack defects of the welded structural parts. Aiming at the problem of cold crack, the method of preheating before welding, heat after emergency after welding and heat after welding with infrared irradiation device is put forward to reduce hardened microstructure and reduce the sensitivity of cold crack. In order to achieve the same purpose as the actual production conditions, 30CrMnSi steel with 1.8mm thickness is used in this paper. CO2 and TIG welding were used to study the effect of preheating, post-heat and post-welding on brittle and hard microstructure. The effect of multiple welding on the microstructure and properties of welded joints was studied, and the effect of heat on weld joints was analyzed. The results show that the effective heat input of CO _ 2 welding is helpful to reduce the hardened microstructure and the hardening tendency and to control the cold cracks. Infrared irradiation with welding can reduce the content of brittle and hard martensite in the completely quenched zone of welded joints, when the distance between the red external irradiating device and the welding torch is 250mm, The maximum microhardness of this area is 511.1HVwhich is 164.1 HVV lower than that of common welding condition, and its tensile strength of 950MPa reaches 91.7 of the base metal. Under the condition of infrared irradiation with welding, the brittle hard microstructure in the complete quenching zone can be reduced effectively, and the cold crack sensitivity can be reduced to a certain extent. Under the condition of using TIG welding, the content of quenched microstructure can be effectively reduced when the infrared welding device is used and the distance is from 50mm to 150mm. However, when the distance of welding torch is larger than 150mm, the temperature is increased after the martensite transformation is completed. The microstructure in this position experienced a tempering, resulting in tempering brittleness, which led to the improvement of cold crack sensitivity. When the preheating temperature is 150 鈩，

本文編號：2114797