本文選題：模具精加工　切入點(diǎn)：硬態(tài)銑削　出處：《哈爾濱理工大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：汽車覆蓋件淬硬鋼模具的制造是汽車生產(chǎn)制造中的重要環(huán)節(jié),然而,淬硬鋼模具精加工時,由于工件硬度較高,加工余量較小,造成刀具與工件之間經(jīng)常出現(xiàn)“滑刀”現(xiàn)象,使得模具最終的尺寸精度和表面質(zhì)量很難保證,增加了后期人工修磨時間。除此之外,淬硬鋼模具精加工采用硬質(zhì)合金刀具加工時,切削效率較低,使得汽車模具的整體制造周期較長。因此,改善淬硬鋼模具精加工中的“滑刀”現(xiàn)象,開展新型刀具材料在淬硬鋼模具精加工中的應(yīng)用研究,對提高汽車覆蓋件模具的加工質(zhì)量及加工效率,進(jìn)而提高汽車制造業(yè)水平具有重要意義。切削刀具在制造過程中切削刃存在一定的鈍圓,使得切削加工存在最小切削厚度,當(dāng)精加工余量選擇不當(dāng)導(dǎo)致實(shí)際切削厚度小于最小切削厚度時,刀具與工件之間將不能進(jìn)行正常的切削,而出現(xiàn)“滑刀”現(xiàn)象。考慮切削刃鈍圓半徑在淬硬鋼模具精加工中的影響,在對銑削加工過程中切削層厚度變化規(guī)律及工件表面形貌分析的基礎(chǔ)上,通過對表面形貌中切削—犁耕—滑擦區(qū)域劃分,提出一種基于銑削加工方式確定最小切削厚度的方法,通過切削實(shí)驗(yàn)及仿真手段對提出的最小切削厚度確定方法的可行性進(jìn)行了驗(yàn)證。在此基礎(chǔ)上,確定了不同硬度淬硬鋼Cr12Mo V的最小切削厚度。采用理論推導(dǎo)方法,建立了考慮切削參數(shù)、工件曲率及刀具變形等因素的淬硬鋼模具凸曲面精加工極限切削深度預(yù)測模型,并通過切削實(shí)驗(yàn)手段對所建立的模型進(jìn)行了驗(yàn)證。此研究成果為淬硬鋼模具精加工余量的選取提供了一個“最小值”,以避免產(chǎn)生“滑刀”現(xiàn)象。通過實(shí)驗(yàn)手段,對比了PCBN刀具與硬質(zhì)合金刀具在銑削加工淬硬鋼方面的切削性能。研究了PCBN刀具斷續(xù)加工淬硬鋼刀具失效機(jī)理,將PCBN刀具斷續(xù)加工淬硬鋼中的刀具破損分為低速性破損與高速性疲勞破損,在揭示其破損機(jī)理的基礎(chǔ)上,給出了避免產(chǎn)生低速性破損的臨界銑削條件。通過對切削實(shí)驗(yàn)中產(chǎn)生疲勞失效刀具的斷口形貌進(jìn)行觀察,揭示熱—力耦合作用下PCBN刀具斷續(xù)加工淬硬鋼疲勞失效機(jī)制,并給出預(yù)防PCBN刀具過早出現(xiàn)疲勞破損的措施。分析了傳統(tǒng)球頭銑刀在加工淬硬鋼模具小曲率型面時的弊端,在此基礎(chǔ)上,設(shè)計開發(fā)了淬硬鋼模具小曲率型面精加工專用雙圓�、裥�、雙圓弧Ⅱ型、sinⅠ型及sinⅡ型PCBN銑刀,并給出了新型PCBN刀具的使用條件。本文以汽車覆蓋件模具常用材料淬硬鋼Cr12Mo V為研究對象,采用理論分析、數(shù)值模擬及切削實(shí)驗(yàn)相結(jié)合的方法,對淬硬鋼模具精加工中“滑刀”現(xiàn)象以及PCBN刀具斷續(xù)加工淬硬鋼機(jī)理等問題進(jìn)行研究。研究成果為提高淬硬鋼模具精加工質(zhì)量及效率,進(jìn)一步實(shí)現(xiàn)汽車覆蓋件淬硬鋼模具的高品質(zhì)加工提供理論依據(jù)及技術(shù)指導(dǎo)。
[Abstract]:The manufacture of hardened steel dies for automobile panels is an important link in automobile manufacturing. However, due to the high hardness of the workpiece and the small machining allowance, the phenomenon of "slippery knife" often occurs between the tool and the workpiece during the finish machining of the hardened steel die. The final dimension accuracy and surface quality of the die are difficult to guarantee, which increases the time of manual grinding. In addition, the cutting efficiency is low when the die of hardened steel is finished with cemented carbide tools. The whole manufacturing period of automobile die is longer. Therefore, the phenomenon of "slipper" in the finish machining of hardened steel dies is improved, and the application of new cutting tool materials in the precision machining of hardened steel dies is studied. It is of great significance to improve the machining quality and efficiency of automobile panel die, and then to improve the level of automobile manufacturing industry. There is a certain blunt circle in the cutting edge of cutting tool in the manufacturing process, which makes the cutting tool have the minimum cutting thickness. When the actual cutting thickness is less than the minimum cutting thickness due to the improper selection of the finishing allowance, the normal cutting between the tool and the workpiece will not be carried out. Considering the influence of the blunt circle radius of cutting edge on the finish machining of hardened steel dies, on the basis of analyzing the thickness of cutting layer and the surface morphology of workpiece during milling, By dividing the cutting, ploughing and sliding friction regions in the surface topography, a method for determining the minimum cutting thickness based on the milling method is proposed. The feasibility of the proposed method for determining the minimum cutting thickness is verified by means of cutting experiments and simulation. On the basis of this, the minimum cutting thickness of hardened steel Cr12Mo V with different hardness is determined. A prediction model of the limit cutting depth for the finish machining of hardened steel die convex surface considering cutting parameters, workpiece curvature and tool deformation is established. The model is verified by cutting experiments. The research results provide a minimum value for the selection of finish machining allowance of hardened steel dies, in order to avoid the phenomenon of "skid knife". The cutting performance of PCBN tool and cemented carbide tool in milling hardened steel was compared. The failure mechanism of PCBN tool in intermittent machining of hardened steel tool was studied. The tool breakage in the intermittent machining of hardened steel by PCBN tool is divided into low speed damage and high speed fatigue damage. The mechanism of tool breakage is revealed. The critical milling conditions to avoid low speed damage are given. By observing the fracture morphology of the tool which produces fatigue failure in cutting experiment, the fatigue failure mechanism of quenched steel produced by PCBN tool under the coupling of heat and force is revealed. The measures to prevent premature fatigue breakage of PCBN cutters are given. The disadvantages of traditional ball end milling cutters in machining the small curvature surface of hardened steel dies are analyzed. The special double circular arc 鈪，

本文編號：1625173