發(fā)布時間：2018-06-18 12:02

  本文選題：GCr15鑄坯 + 徑向熱輾擴　； 參考：《武漢理工大學(xué)》2015年碩士論文

【摘要】：中小型軸承環(huán)件(套圈)作為中小型軸承的基體組件,廣泛應(yīng)用于各類機械設(shè)備領(lǐng)域。中小型軸承環(huán)件的傳統(tǒng)塑性加工工藝主要包括鍛造制坯工序(下料、鐓粗、沖孔等)和徑向輾擴工序。而軸承鑄坯徑向熱輾擴成形工藝,是鑄輾復(fù)合新工藝中針對中小型軸承環(huán)件成形的一種低碳高效成形的新工藝。新工藝將傳統(tǒng)中小型環(huán)件成形工藝中冗長復(fù)雜的鍛造制坯改進為鑄造制坯,大幅度縮短了工藝流程,提高了材料利用率,降低了廢氣排放,具有很高的經(jīng)濟效益和環(huán)境效益。但目前,鑄坯徑向熱輾擴新工藝的研究還處于起步階段,國內(nèi)外研究基本處于空白,相應(yīng)的指導(dǎo)理論不足,還難以得到應(yīng)用與推廣。針對此現(xiàn)狀,本研究對GCr15軸承鑄坯徑向熱輾擴工藝進行了相關(guān)基礎(chǔ)研究。研究重點圍繞GCr15軸承鑄坯熱輾擴過程中鑄態(tài)組織轉(zhuǎn)變和鑄造缺陷改善兩大關(guān)鍵問題開展,以期為新工藝的進一步研究與應(yīng)用提供一定的理論指導(dǎo)和科學(xué)依據(jù)。對于鑄態(tài)組織轉(zhuǎn)變方面,通過數(shù)值模擬技術(shù)建立了GCr15鑄坯徑向熱輾擴微觀組織有限元模型,研究了鑄坯熱輾擴過程中微觀組織的演變行為。首次提出了晶粒細(xì)化極限的概念,并對晶粒細(xì)化極限進行了理論探究,從應(yīng)變和Z-H系數(shù)兩個方面對晶粒細(xì)化極限進行了討論。晶粒細(xì)化極限的提出對于鑄態(tài)環(huán)件熱輾擴過程中晶粒尺寸的控制具有非常重要的作用。開展了GCr15鑄坯徑向熱輾擴工藝實驗,對成形后環(huán)件進行了金相測試,探究了不同變形量下環(huán)件晶粒尺寸的演變規(guī)律。研究結(jié)果對于鑄坯熱輾擴過程中晶粒尺寸的控制具有重要意義。對于鑄造缺陷改善方面,以球形孔洞為研究對象,通過數(shù)值模擬技術(shù)建立了GCr15鑄坯球形孔洞有限元模型。通過建立球形孔洞局部坐標(biāo)系,研究了球形孔洞的基本演變行為,并探究了影響球形孔洞演變的主要因素,揭示了工藝參數(shù)對球形孔洞演變的影響。通過比較球形孔洞和柱形通孔的演化行為,提出了球形孔洞演變的理論假設(shè),并對假設(shè)進行了驗證,以此建立了球形孔洞的形狀變化預(yù)測模型。設(shè)計并開展了孔洞演變實驗,進一步探究了鑄坯孔洞缺陷在熱輾擴過程中的演變規(guī)律。
[Abstract]:As the base assembly of medium and small bearing, small bearing ring (ring) is widely used in various fields of machinery and equipment. The traditional plastic processing technology of small and medium bearing ring mainly includes forging process (blanking, upsetting, punching etc.) and radial rolling process. The radial hot rolling forming process of bearing billet is a new low carbon high efficiency forming process for small and medium bearing ring forming in the new casting rolling compound process. The new process improves the long and complicated forging billets in the traditional forming process of small and medium-sized ring parts into casting billets, greatly shortens the process flow, improves the utilization ratio of materials, reduces the exhaust gas emissions, and has high economic and environmental benefits. However, at present, the research on the new technology of radial hot rolling is still in its infancy, the research at home and abroad is basically blank, the corresponding guiding theory is insufficient, and it is difficult to be applied and popularized. In view of this situation, this research has carried on the correlation basic research to the GCr15 bearing billet radial hot rolling technology. The research focuses on the two key problems of as cast structure transformation and casting defect improvement during hot rolling of GCr15 bearing billet in order to provide certain theoretical guidance and scientific basis for the further study and application of the new technology. For the transformation of as-cast structure, the finite element model of the microstructure of GCr15 billet was established by numerical simulation, and the evolution of microstructure during hot rolling was studied. The concept of grain refinement limit is put forward for the first time, and the grain refinement limit is studied theoretically. The grain refinement limit is discussed from two aspects: strain and Z-H coefficient. The grain refinement limit is very important for the control of grain size in the hot rolling process of as-cast ring. The experiment of GCr15 billet radial hot rolling process was carried out. The metallographic test of the formed ring was carried out, and the evolution law of the ring grain size under different deformation quantities was investigated. The results are of great significance to the control of grain size during hot rolling of billet. For the improvement of casting defects, the finite element model of spherical cavity in GCr15 billet was established by numerical simulation. The basic evolution behavior of spherical voids was studied by establishing local coordinate system of spherical voids, and the main factors affecting the evolution of spherical voids were explored, and the influence of technological parameters on the evolution of spherical voids was revealed. By comparing the evolution behavior of spherical cavity and cylindrical through hole, the theoretical hypothesis of spherical hole evolution is proposed, and the hypothesis is verified, and a prediction model of spherical cavity shape change is established. The hole evolution experiment was designed and carried out, and the evolution law of cavity defect in hot rolling process was further explored.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TH133.3;TG306

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本文編號：2035415