Effect of MQL on the tool life of small twist drills in deep-hole drilling

Drilling of deep and small boreholes using twist drills has to be considered as one of the most difficult metal cutting operations. There are many reasons for this, one of them being that the cutting fluid has to be supplied externally. This research work investigates in how far the manner of supplying and the type of minimum quantity lubricant have an effect on the tool life of coated and uncoated high-speed steel twist drills of 1.5 mm diameter. Deep-hole drilling is performed as the holes, drilled into plain carbon steel, had a depth of 10 times the diameter. The feasibility of dry machining as an appropriate alternative to MQL in deep-hole drilling has also been investigated. This work shows that, compared to a continuous supply of the minimum quantity lubricant, a discontinuous supply brings about a significant reduction in tool life, especially in the case of heat-sensitive drills. With respect to the type of minimum quantity lubricant, a low-viscous type with a high cooling-capability gave rise to a notably prolonged tool life. It is also shown that dry drilling is associated with strongly accelerated tool wear for most of the twist drills tested, resulting in a significant reduction in tool life.     

Chip thickening in deep-hole drilling

In conventional turning and milling cutting process models, chips are free of external forces after leaving the cutting area. However, in a drilling process, chip flowing is constrained by the drill flute, causing the change of chip shape and drilling forces. In this research, it is found that when drilling deep holes, the chip thickness increases as drilling progresses deeper into the workpiece. It is also found that during a deep-hole drilling process a significant part of the drilling force increase is due to the chip thickening effect. An analytical model was developed to predict the force increase caused by chip thickening. Experiments have been carried out to verify the model.     

Effects of support misalignments in deep-hole drill shafts on hole straightness

This work investigates the effect of drill shaft support misalignment on hole straightness in relation to the various control factors. Misalignments occur in machine spindles, intermediate supports and pilot bushings. Equations for axial hole straightness deviation are derived herein using the Euler column theory, and experiments are performed using Gundrill and BTA deep-hole drilling systems. Simulation results, Sakuma's method and experimental examinations are also presented. Taguchi methods and statistical techniques are used to formulate the experimental layout, analyze the effect of each control factor on the results, and optimize the setting for each control factor. Further experiments then verify these estimates. Six control factors were used in a modified L8 orthogonal array design. The confirmatory experiments revealed an average straightness deviation within the 95% confidence interval.     

深孔加工切削液造成BTA钻杆涡动分析

利用BTA钻杆内切削液的Reynolds方程,得出钻杆所受流体力与钻杆转速、涡动和挤压效应之间的关系。分析深孔加工钻杆产生涡动的原理,指出促进钻杆正进动的流体分力是钻杆发生涡动的根本原因。模拟并分析了在不同时刻钻杆圆涡动形态,指出在只受到流体力时,钻杆可以稳定地运动。研究钻杆的反进动,揭示挤压油膜阻尼器的工作原理。利用MATLAB软件模拟分析添加挤压油膜阻尼器前、后钻杆的运动情况,证明挤压油膜阻尼器可以显著减小钻杆涡动。     

Theoretical and experimental determination of tool life in hot machining of austenitic manganese steel

In this study, an expression for the tool life of a sintered carbide tool machining heated austenitic manganese steel was developed. The influence of surface temperature, cutting speed, feed rate, and depth of cut on the tool life were investigated. Afterwards, an expression for the effects of cutting conditions on tool life were determined using a mathematical model developed by a factorial regression method.     

薄壁管件液压成形工艺改进与疲劳寿命分析

通过对现有U形薄壁管件液压成形工艺的分析,提出应对壁厚不均和疲劳寿命短两方面进行改进;在基于被动液压成形理论分析计算的基础上,提出具体工艺改进方案,并对被动液压成形加载曲线合理区间进行了分析;基于LS-DYNA动力显式有限元分析软DYNAFORM5.6,对薄壁管被动液压成形进行模拟仿真,对改进前后工艺进行对比分析,并结合仿真结果,对改进前后成形工艺加工工件的疲劳寿命进行对比,分析对比结果表明,改进后工艺可显著提高工件的疲劳寿命。     

H型钢初轧机推床翻钢机技术改进

对H型钢热连轧生产线原推床翻钢机在使用过程中出现的问题进行了分析,对其重要部件即翻钢机、推床本体、推床护板等做了技术改进,从而解决了原设备在生产中存在的不足,使翻钢机的翻钢时间从原来的21s减少为2.3s,大大提高了轧制节奏,降低了维修成本,提高了产能。     

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为了探讨高锰含量对微合金钢性能的影响及其夹杂物存在形态,采用低碳+钒铁微合金化工艺生产一种高强度热轧型钢,锰质量分数为1.50%~1.60%。结果表明:产品屈服强度为440~460 MPa,抗拉强度为600~620 MPa,金相组织为铁素体+团状珠光体,带状组织3~4级,晶粒度为7~8.5级,但是锰提高了团状珠光体的相对量,削弱了钢材的低温冲击韧性。锰除固溶于铁基体中外,多以含锰夹杂物的形式存在,主要包括片状硫化锰、球形复合型夹杂物和纺锤体形复合型夹杂物。     

Reactive wetting during hot-dip galvanizing of high manganese alloyed steel

The present study discusses reactive wetting during hot-dip galvanizing of high Mn alloyed steel (X-IP1000, 23 wt.% Mn) and is focused on investigating the influence of the metallic Mn concentration in the steel bulk composition on phase formation at the interface steel/coating. Samples were in-line bright annealed (1100 °C/ 60 s in N2-5%H2 at DP −50 °C) prior hot-dipping to avoid external MnO on the steel surface. This approach was applied to avoid influencing the wetting reaction by an aluminothermic MnO reduction, because this is considered to lead to an unwanted zeta-phase (FeZn13) formation in the coating by hot-dipping of Mn alloyed steels (< 5.0 wt.% Mn). The influence of hot-dipping parameters, which are contributing to the kinetics of the wetting reaction, was examined in terms of varying bath-Al content (0.17 and 0.22 wt.%), bath temperature (440-500 °C) and strip entry temperature (420-520 °C). The structure and chemical composition of both galvanized coating and interface steel/coating were characterized. While external MnO was verifiably avoided, brittle zeta-phase distinctively appeared at the interface steel coating together with the typical Fe₂Al₅ phase. This shows that the model of aluminothermic MnO reduction failed in the present case. This study suggests an alternative model explaining the appearance of zeta-phase with the removal of bath-Al by metallic Mn, which is dissolved out of the steel bulk into the Zn bath. The present investigation shows that alloying elements in the steel bulk may influence coating quality not only “indirectly” by external formation of nonwettable oxides, but also “directly” by influencing phase equilibria and kinetics of the wetting reaction. Understanding these phenomena will improve processing of (high) alloyed steel concepts as well as industrial Zn bath management.     

15CrMoG钢管的寿命评估新方法

采用高温加速时效的方法模拟15CrMoG钢管珠光体组织球化的演变过程并测试不同球化程度下的布氏硬度,结合现场检测对电站锅炉15CrMoG钢管进行硬度和球化程度分析。基于Matlab软件模拟建立硬度与珠光体球化之间的关系模型,提出15CrMoG珠光体组织的球化与温度和时间之间的关系公式,即温度和时间对组织球化进程的影响,进而提出该钢管寿命评估的新方法。     

提高大型板坯连铸机通钢能力和备件寿命探讨

随着去产能和打击地条钢工作的深入,2018年中国大陆钢产量创造了历史新纪录,重庆钢铁股份有限公司司法重整成功后的第一年就开始实施满产满销战略,取得了良好成效。如何在设备备件寿命提高的基础上提高炼钢厂(一系列)的板坯连铸机通钢能力,是炼钢厂的一项重要工作。从人、机、料、法、环、测6个方面对其进行了剖析,提出了生产、技术、设备3个方面各自需要开展的工作,以此推动连铸工序设计目标的实现,促进炼钢产能的进一步达标。     

含焊接缺陷的30CrMnSiNi2A钢焊接件的疲劳寿命估算

本文分析了焊接缺陷对超高强度钢３０ＣｒＭｎＳｉＮｉ２Ａ焊接件疲劳寿命的影响，给出了定理评估含焊接缺陷的焊接件疲劳性能的方法，焊接缺陷可分成类裂纹型和非裂纹型两类，前者的作用与裂纹相当，含这类缺陷的焊接件寿命近似等于裂纹扩展寿命；后者的作用则类似缺口，含这类缺陷的焊接件寿命为裂纹起始与扩展寿命之和，裂纹扩展寿命可用断裂力学的方法计算，始裂寿命则可用材料的始裂寿命公式计算，但在计算中要考虑表面状态修正     

65Mn钢弹簧片断裂分析及工艺改进

某型产品使用的65Mn钢弹簧片检测弹力时发现在波峰位置出现断裂,经化学成分、显微组织、显微硬度检测以及加工过程分析,对弹簧片断裂原因进行了分析,并对工艺做了优化。结果表明,弹簧片由于淬火温度高,淬火硬度大,且淬火后低温回火温度低,淬火应力消除不充分,致使弹簧片高温回火时安装夹具过程中,弹簧片在轴向压应力以及淬火残留应力综合作用下产生微裂纹,后续强压处理时微裂纹扩展转变,发生脆性断裂。采用改进工艺815 ℃淬火+280 ℃低温回火+390 ℃高温回火处理后,弹簧片硬度合格,断口均为100%韧性断口,再未出现脆性断裂现象。     

焊接残余应力对Invar钢疲劳寿命影响分析

利用有限元软件MSC.Marc计算了液化石油天然气船液舱Invar钢薄膜的焊接温度场和残余应力场,并计算了焊接残余应力与液体晃荡压力耦合条件下焊缝处的疲劳寿命.结果表明,焊缝表面中心线上的节点的纵向残余应力可达298.1 MPa左右,焊缝纵向残余应力的峰值可达328.3 MPa左右,高于Invar钢的室温屈服强度280.1 MPa.由于焊接残余应力的存在,Invar钢薄膜焊缝的疲劳寿命约由2.1×106降低到1.7×105.     

热浸镀铝硅钢板表面点状缺陷分析及改进

为提高铝硅镀层钢板表面质量,利用光学显微镜(OM)、扫描电镜(SEM)及能谱(EDS)对镀铝硅钢板表面出现的点状缺陷的显微形貌及成分进行分析.结果表明,铝硅镀层钢板表面产生的点缺陷主要分为4类,第I类点缺陷成分主要为Al-Si氧化物和氧化锌,由铝渣及锌灰粘附在镀层表面所致;第II类点缺陷产生原因为镀层表面压入铝渣或异物...     

表面渗钛的镀锌钢板点焊电极寿命试验研究

对Cr-Zr-Cu合金的镀锌钢板点焊电极进行了表面渗钛处理，通过点焊电极寿命试验观测了表面渗钛处理前后镀锌钢板点焊的表面质量和电极端面状况。试验结果表明，采用表面渗钛可以提高镀锌钢板点焊电极的耐磨性和热稳定性，从而延长了电极的寿命。     

辅磨料金刚石地质钻头试验研究

本文采用五种粒度金刚石作为辅磨料,共设计了13种不同配方的孕镶金刚石钻头进行钻进混凝土的试验,探讨了在相同胎体成份下钻头所加入辅磨料的参数设计对其性能的影响。本研究发现合适粒度和浓度的辅磨料添加,不但可以提高钻头的寿命,而且也能提高其锋利性。室内试验研究表明:加入粒度为120/140目、浓度为6%左右的辅磨料时,能使钻头在钻进混凝土时,效率和寿命分别提高40%和150%。     

镀锌钢板点焊电极寿命预测

采用连续点焊试验与数值模拟相结合的方法预测电极寿命,即利用镀锌钢板连续点焊试验得出电极端面直径随焊接点数增加的规律,并用ANSYS软件模拟不同电极端面直径下点焊区域温度场,得出对应的熔核直径.综合试验及模拟结果得出焊接点数与熔核直径的关系,在定义了保证焊点质量的临界熔核直径情况下,即可得出相应的临界电极端面直径和连续点焊可焊点数,从而预测电极寿命.结果表明,两种方法得出的熔核直径的误差不超过15%.此方法对实际生产过程中的电极修整及更换周期制定具有一定的指导作用.     

无磁钻铤用Cr-Mn-Ni-N系高氮钢平衡凝固相变与析出行为

借助Thermo-Calc软件对无磁钻铤用Fe-(15~25)Cr-(15~25)Mn-(0~5)Ni-(0~1)Mo-(0~1)N-(0~0.8)C多元系高氮钢在凝固和冷却过程中的相变及析出行为进行研究。使用Thermo-Calc软件中的TCFE9数据库对该钢相图的垂直截面图进行计算,分析了Cr、Mn、Ni、Mo、N及C元素对无磁钻铤用高氮钢凝固及冷却过程中相变的影响,并得到了平衡凝固相变路径图。结果表明,增加Cr、Mn含量可显著提高合金中氮的溶解度,Mo元素可以微弱提高氮的溶解度,Ni、C元素显著降低氮的溶解度。Ni、C和N含量提高可扩大单相奥氏体相区,具有稳定奥氏体的作用,Cr、Mo与Mn元素缩小单相奥氏体相区,具有稳定铁素体的作用。N元素可以促进M₂(C,N)相析出,使M₂₃C₆相析出受到抑制。Cr、Mn元素可以促进Sigma相析出,C、N元素抑制Sigma相析出。M₂₃C₆相的析出主要受C含量的影响,随着C含量的升高,M₂₃C₆相的析出温度显著升高。     

不锈钢板冷轧机轧制油过滤器寿命探讨

通过对油在滤芯内流动的力学特性分析，得出在其他条件不变的情况下，通过过滤系统的流量是影响滤芯寿命的主要因素，流量增加1倍，寿命减少1／2以上。此结果在宝钢集团宁波宝新不锈钢有限公司二十辊不锈钢板冷轧机上进行试验时，得到证实。