發(fā)布時間：2018-05-19 15:32

  本文選題：ACR銅管 + 鑄軋法��； 參考：《沈陽理工大學》2017年碩士論文

【摘要】：ACR(Air Conditioner and Refrigerator)銅管被廣泛用作工業(yè)冷凝器、蒸發(fā)器和換熱系統(tǒng)中重要外部聯(lián)接管件,其直徑大于等于Φ16mm。鑄軋法具有初始投入少、生產(chǎn)成本低和加工效率高等優(yōu)點,因此,在保證產(chǎn)品質(zhì)量的前提下,很多企業(yè)考慮采用鑄軋法替代擠壓法加工大中口徑ACR銅管,以解決傳統(tǒng)擠壓工藝生產(chǎn)的銅管長度和產(chǎn)量受到限制的問題。本文研究了加工工藝改變對ACR銅管成形質(zhì)量的影響,并分析了ACR銅管實際加工過程中出現(xiàn)的質(zhì)量缺陷問題。針對某銅管廠生產(chǎn)的規(guī)格為Φ19×1 mm的ACR銅管,分別從鑄軋法和擠壓法生產(chǎn)現(xiàn)場進行追蹤取樣,獲得不同道次的ACR銅管,并從化學成分、微觀組織、力學性能、表面質(zhì)量和尺寸精度等方面進行對比分析,綜合評價了兩種工藝方法對ACR銅管成形質(zhì)量的影響。研究表明采用鑄軋法生產(chǎn)ACR銅管在化學成分、微觀組織演變和力學性能方面都與原工藝相近,但鑄軋法生產(chǎn)的初始管材組織分布均勻,晶粒細小。隨著加工道次的增加,鑄軋銅管的延伸率和顯微硬度波動幅度較小,采用鑄軋法可以提高成品銅管的力學性能穩(wěn)定性。改用鑄軋法加工的ACR銅管表面光亮度高、粗糙度低、表面平均殘余應力遠小于擠壓管,并且鑄軋ACR銅管的尺寸精度高,能夠顯著提高產(chǎn)品合格率。針對ACR銅管加工過程中出現(xiàn)“表面裂紋”和“跳車紋”質(zhì)量缺陷,采用實驗分析、理論分析和有限元模擬等方法加以分析論證。研究表明表面裂紋的形成機理是先沿晶斷裂產(chǎn)生熱裂紋,然后穿晶斷裂形成冷裂紋,其主要形成原因是結(jié)晶器堵塞,導致銅液中有害氣體不能及時排出,使其在連鑄管材表層形成裂紋源,同時由于結(jié)晶器內(nèi)表面粗糙,拉坯阻力增加,導致管材表面拉裂并向內(nèi)部不斷擴展。銅管表面跳車紋實質(zhì)上是拉拔過程中產(chǎn)生的壁厚不均勻缺陷,其形成機理是游動芯頭超過前后極限位置造成拉拔系統(tǒng)失穩(wěn),當芯頭超過前極限位置,內(nèi)外模具過度擠壓管材形成局部縮頸;當芯頭超過后極限位置,空拉管材使壁厚增加,造成管材表面材料局部突起。通過有限元模擬得到優(yōu)化的拉拔工藝條件:摩擦系數(shù)為μ=0.05、拉拔速度為ν=90m/min、過渡圓弧半徑R=5mm,拉拔外模錐角α=15°和芯頭錐角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 偽 15 擄and core cone angle 10 擄.
【學位授予單位】：沈陽理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG339;TG379

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