控制30CrMnSi钢接头焊接冷裂纹的研究

发布时间：2018-07-11 10:19

  本文选题：30CrMnSi + 焊接冷裂纹　； 参考：《南昌航空大学》2015年硕士论文

【摘要】：某一重要构件使用30CrMnSi钢生产,但是,在焊接的过程中出现了一系列问题。其中大量出现的冷裂纹使得该焊接结构件无法满足该工厂的缺陷率要求,造成了大量的成本浪费,为此对该焊结构件焊接冷裂纹缺陷的控制显得十分有必要。针对冷裂纹这一问题,提出了使用红外照射装置焊前预热、焊后紧急后热以及随焊后热的方法,减少淬硬组织,以达到降低冷裂纹敏感性的目的。为了达到与实际生产条件相同的目的,本文使用1.8mm厚的30CrMnSi钢,采用该结构中占多数的对接形式。分别采用CO2气体保护焊(CO2焊)和钨极氩弧焊(TIG焊)进行试验,研究了预热、及时后热和随焊后热对脆硬组织及影响规律,同时,研究了多次补焊对焊接接头组织及性能的影响规律,分析了焊后及时后热对补焊接头的作用。研究结果表明:较小的CO2焊有效热输入有利于减少淬硬组织、降低淬硬倾向而控制焊接冷裂纹。使用随焊红外照射可以降低焊接接头完全淬火区组织中脆硬组织片状马氏体的含量,当红外照射装置与焊枪的距离为250mm时,该区域的最高显微硬度为511.1HV,较普通焊接条件降低了164.1HV,其抗拉强度为950MPa达到了母材的91.7%。在该随焊红外照射条件下,可以有效地减少了完全淬火区中的脆硬组织,在一定程度上降低了冷裂纹敏感性。在使用TIG焊的条件下,采用红外随焊装置且距离为50mm到150mm时均能有效的减少淬硬组织的含量,但是当焊枪距离大于150mm时,由于在马氏体转变完成后进行了升温,使得该位置的组织经历了一次“回火”,产生回火脆性,导致冷裂纹敏感性的提高。当预热温度为150℃时,完全淬火区的最高显微硬度为470HV,较不预热条件下的560HV有了明显的降低。当及时后热时间为6min时,其对降低冷裂纹敏感性的作用最为明显,随着后热时间的增加,由于回火作用更加明显,冷裂纹敏感性有所增加。使用TIG焊对缺陷进行补焊,对三种不同补焊形式进行了研究,对不同补焊次数的影响进行了分析。表明随着补焊次数的增加,三种不同的补焊形式的焊接接头抗拉强度均呈现出下降的趋势,接头软化也出现恶化的趋势。三种补焊方式中,连续气孔补焊对接头的影响最大,焊缝中心气孔补焊和熔合线补焊对接头的性能影响较小。补焊后使用及时后热可以有效的降低完全淬火区的淬硬组织含量,提高接头抗冷裂性能。
[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，

本文编号：2114797