ACR铜管加工工艺与质量缺陷的研究

发布时间：2018-05-19 15:32

本文选题：ACR铜管 + 铸轧法　；参考：《沈阳理工大学》2017年硕士论文

【摘要】：ACR(Air Conditioner and Refrigerator)铜管被广泛用作工业冷凝器、蒸发器和换热系统中重要外部联接管件,其直径大于等于Φ16mm。铸轧法具有初始投入少、生产成本低和加工效率高等优点,因此,在保证产品质量的前提下,很多企业考虑采用铸轧法替代挤压法加工大中口径ACR铜管,以解决传统挤压工艺生产的铜管长度和产量受到限制的问题。本文研究了加工工艺改变对ACR铜管成形质量的影响,并分析了ACR铜管实际加工过程中出现的质量缺陷问题。针对某铜管厂生产的规格为Φ19×1 mm的ACR铜管,分别从铸轧法和挤压法生产现场进行追踪取样,获得不同道次的ACR铜管,并从化学成分、微观组织、力学性能、表面质量和尺寸精度等方面进行对比分析,综合评价了两种工艺方法对ACR铜管成形质量的影响。研究表明采用铸轧法生产ACR铜管在化学成分、微观组织演变和力学性能方面都与原工艺相近,但铸轧法生产的初始管材组织分布均匀,晶粒细小。随着加工道次的增加,铸轧铜管的延伸率和显微硬度波动幅度较小,采用铸轧法可以提高成品铜管的力学性能稳定性。改用铸轧法加工的ACR铜管表面光亮度高、粗糙度低、表面平均残余应力远小于挤压管,并且铸轧ACR铜管的尺寸精度高,能够显著提高产品合格率。针对ACR铜管加工过程中出现“表面裂纹”和“跳车纹”质量缺陷,采用实验分析、理论分析和有限元模拟等方法加以分析论证。研究表明表面裂纹的形成机理是先沿晶断裂产生热裂纹,然后穿晶断裂形成冷裂纹,其主要形成原因是结晶器堵塞,导致铜液中有害气体不能及时排出,使其在连铸管材表层形成裂纹源,同时由于结晶器内表面粗糙,拉坯阻力增加,导致管材表面拉裂并向内部不断扩展。铜管表面跳车纹实质上是拉拔过程中产生的壁厚不均匀缺陷,其形成机理是游动芯头超过前后极限位置造成拉拔系统失稳,当芯头超过前极限位置,内外模具过度挤压管材形成局部缩颈;当芯头超过后极限位置,空拉管材使壁厚增加,造成管材表面材料局部突起。通过有限元模拟得到优化的拉拔工艺条件:摩擦系数为μ=0.05、拉拔速度为ν=90m/min、过渡圆弧半径R=5mm,拉拔外模锥角α=15°和芯头锥角β=10°。
[Abstract]:ACR(Air Conditioner and Refrigerator) copper pipe is widely used in industrial condenser, evaporator and heat transfer system. Its diameter is greater than or equal to 桅 16mm. The cast rolling process has the advantages of low initial investment, low production cost and high processing efficiency. Therefore, under the premise of ensuring the product quality, many enterprises consider using casting and rolling method instead of extrusion method to process large and medium diameter ACR copper pipes. In order to solve the problem that the length and output of copper tube produced by traditional extrusion process are limited. In this paper, the influence of processing technology change on the forming quality of ACR copper tube is studied, and the quality defects in the process of ACR copper tube processing are analyzed. According to the ACR copper pipe with 桅 19 脳 1 mm size produced by a copper pipe factory, the ACR copper pipe with different passes was obtained by tracing and sampling from the production site by casting and extrusion methods, and the chemical composition, microstructure and mechanical properties of the ACR copper pipe were obtained. The surface quality and dimension precision were compared and analyzed, and the influence of two kinds of process methods on the forming quality of ACR copper tube was evaluated synthetically. The results show that the chemical composition, microstructure evolution and mechanical properties of ACR copper pipes produced by casting and rolling process are similar to those of the original process, but the initial pipes produced by casting rolling process have uniform microstructure distribution and fine grain size. With the increase of the number of passes, the range of elongation and microhardness of cast rolled copper pipe is small, and the mechanical property stability of finished copper tube can be improved by casting rolling method. The ACR copper tubes manufactured by casting and rolling method have high surface brightness and low roughness, the average surface residual stress is much smaller than that of extruded tubes, and the dimension accuracy of cast rolled ACR copper pipes is high, which can significantly improve the qualified rate of the products. In view of the quality defects of "surface crack" and "car jump pattern" in the process of ACR copper pipe processing, the experimental analysis, theoretical analysis and finite element simulation are used to analyze and demonstrate the defects. The results show that the formation mechanism of surface crack is that the thermal crack is formed by the intergranular fracture and then the cold crack is formed by the transgranular fracture. The main reason is that the mold is blocked and the harmful gas in the copper liquid can not be discharged in time. The crack source is formed on the surface of continuous casting pipe, and the inner surface of mould is rough and the resistance of drawing billet is increased, which leads to the surface crack of tube and expanding to the inside. The car-jumping pattern on the surface of copper pipe is actually a non-uniform defect of wall thickness produced in drawing process. The forming mechanism is that the moving core head exceeds the limit position before and after, which results in the instability of drawing system, and when the core head exceeds the front limit position, the mechanism is that when the core head exceeds the front limit position, When the core head exceeds the rear limit position, the wall thickness of the tube is increased by empty drawing, which results in the local protruding of the surface material of the pipe. The optimized drawing process conditions are obtained by finite element simulation: friction coefficient 渭 0. 05, drawing speed 90 m / min, transition arc radius R5 mm, cone angle 伪 15 掳and core cone angle 10 掳.
【学位授予单位】：沈阳理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG339;TG379

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