车削加工AISI 1045工件的切削热建模与仿真研究

车削过程中的切削热关系到整体的切削机理、刀具寿命以及加工性能,目前针对切削热的建模方法有很多,但是实际应用过程中却存在很多的问题,文章建立了一种车削加工AISI 1045工件的温度预测解析模型,模型中对三个关键的切削区域进行了快速估计,模型同时考虑了切削参数与材料属性,通过解析模型的计算与有限元仿真方法的对比,并将解析模型的结果与Trigger方法进行了对比,验证了文中提出模型的有效性。

Kinetics modeling for austenite transformation in AISI 1045 steel during rapid heating under high frequency electromagnetic field

To investigate the effect of alternating magnetic field on austenite transformation process in the case of rapid heating,the austenite kinetics model of AISI 1045 steel was built for spot continual induction hardening(SCIH)process.The results shows that the effect of alternating magnetic field on austenite transformation fraction reaches the maximum(about 3%)when heating rate is the lowest.Relatively low magnetic flux density still has a certain effect on the austenite transformation process during the SCIH process.Concave surface structure can reduce the influence scope of alternating magnetic field on surface in all cases and the minimum influence scope appears when the feed path of inductor is longitudinal.Convex surface structure can minimize the influence scope of alternating magnetic field in depth when the feed path of inductor is longitudinal.The austenite distribution of transitional region on surface for horizontal movement is more uniform than that for longitudinal movement.The austenite distribution of transitional region in depth for longitudinal movement is more uniform than that for horizontal movement.The simulated results are consistent with the experimental results and the austenite transformation kinetics model developed for SCIH process is valid.

单颗磨粒磨削AISI 1045钢的磨削力实验研究

采用回转直径为400 mm的单颗PCBN磨粒对AISI 1045钢进行磨削实验。使用Kistler 9119AA2型三维测力仪实时测量磨削力,借助扫描电子显微镜(SEM)观察工件表面质量和磨削形态。研究了磨削工艺参数对磨削力的影响规律,并就磨削速度对表面质量的影响进行了分析。结果表明:磨削工艺参数对磨削力有显著的影响,磨削力随磨削线速度增大而减小,随磨削深度增大而增大,随磨粒前角增大而减小;磨削线速度越大,工件表面质量越好,毛刺越少;负前角单颗磨粒磨屑形态主要有卷曲形和螺旋形两种。

Effect of laser-discrete-quenching on bonding properties of electroplated grinding wheel with AISI 1045 steel substrate and nickel bond

To improve the bonding strength between the nickel bond and the hub of the electroplated diamond grinding wheel,a hybrid technique was proposed to combine laser prequenching steel substrate and post-electroplating nickel.To validate the effectiveness of the proposed technique,AISI 1045 substrate was nickel-coated.The bonding properties between the electroplated nickel coating and substrate with or without laser-discrete-quenching were discussed comparatively by scratch,indentation,and thermal shock tests.The results show that the prequenching treatment leads to phase transformation of AISI 1045 microstructure from the mixed pearlite and ferrite phases into the martensitic phase.Since the martensitic phase is characterized as a high corrosion resistance,the interface of substrate/coating is smooth and flat in the prequenched zone,and the coating is bonded well with the steel substrate.In contrast to the steel substrate without pre-quenching treatment,the proposed technique significantly enhanced the bonding strengths of the electroplated nickel-coating.On one hand,the average hardness of electroplated nickel-coating on the laser pre-quenched zone is increased by 18.7%,and the scratch depth with the same load become narrower and shallower.On the other hand,the coefficient of friction(CoF)and the vibration amplitude are reduced,and the coating is bonded effectively with the substrate to inhibit the crack initialization at the interface.This prevents effectively the coating from peeling off and improves significantly the thermal shock resistance property.

硬质合金铣刀刃口优化及切削寿命研究

刀具切削寿命是高端制造领域中重要的评价环节,能够直接影响切削效率与企业效益。刀具的宏观几何结构是影响刀具切削寿命的重要因素之一,而刀具微刃口作为工件与刀具的直接接触区域,其刃型结构也是影响刀具寿命的关键因素。本文通过立式旋转钝化法制备了具有对称型与非对称型微刃几何的硬质合金铣刀,并通过AISI1045钢铣削实验进行对比分析,研究了不同微刃结构对铣刀寿命的影响,实现了刀具微刃结构的优化设计。实验结果表明:经钝化处理的微刃表面形貌质量得到显著提升,前后刀面钝化速率的差值是形成不同微刃结构的关键因素,不同微刃结构下的后刀面磨损以沟纹磨损为主,优化后的铣刀能够有效抑制刀具崩刃,减缓刀具磨损速率,形状因子K=0.5、钝圆半径R=11μm的优化方案寿命提升最为明显,增益高达25%。

基于权重粒子群算法的工件铣削温度研究

为研究铣削加工中工件的温度分布规律,推导其热传导数学模型,提出应用权重粒子群算法(Weighted particle swarm optimization,WPSO)开展时变热流密度辨识的方法,并结合试验数据对AISI1045钢在特定工况下的温度分布情况进行分析。结果表明,铣削过程中的界面热流密度呈3个阶段的非线性变化;切削初期存在缓慢温升的平台期,渡过平台期后,工件与刀具相接触部分的温度急剧上升,最高温度可达到860℃左右;从试验结果与解析结果的对比来看,两者误差的最大值约为11.06%,结果基本吻合。研究表明所提出的方法可以较为准确研究铣削加工过程中工件的温度分布情况。

45^#钢／GCr15钢摩擦副的滚动磨损特性研究

通过对液压式试验台夹具进行改造 ,研制了往复滚动试验装置 ,以实现对运动位移和表面摩擦力的精确控制 .利用该装置考察了表面摩擦力变化对 45 #钢 / GCr15钢摩擦副滚动磨损特性的影响 .结果表明 :随着表面摩擦力的增加 ,钢的滚动磨损明显加剧 ,磨损机制亦发生变化 .

偏压对45钢离子渗氮行为的影响

在直流脉冲等离子体渗氮炉内放置一由双层圆筒组成的活性屏,双层圆筒与阴极相接,由于其直径不同可以产生空心阴极放电。将45钢试样放置在活性屏内,一组试样处于悬浮状态,另一组试样施加负偏压(50～150V),同时在400～550℃下进行离子渗氮处理。并用金相显微镜、XRD和显微硬度计对渗氮层进行对比分析。结果表明:偏压显著影响渗氮层的组织结构和性能。偏压试样渗氮层与悬浮试样相比,具有更厚的化合物层,表面硬度更高,扩散层更厚。

丙烷浓度对45钢离子碳氮共渗的影响

首次以丙烷作为供碳剂对45钢进行离子碳氮共渗。利用金相显微镜、X射线衍射仪和显微硬度计研究了丙烷浓度对试样截面形貌、物相组成和表面硬度的影响。结果表明:随丙烷浓度的增加,化合物层厚度和表面硬度均呈现先增大后减小的趋势。当丙烷浓度为1.5%时,510℃离子碳氮共渗4h后,化合物层厚度和表面硬度分别达到最大值40μm和779HV0.05,同时得到以ε相为主,并伴有极少量渗碳体的最优物相组成。当丙烷浓度超过1.5%时,化合物层厚度和表面硬度均下降,这是由于渗碳体相含量随丙烷的增加而增加,并当丙烷浓度为2.5%时渗碳体成为主要物相,从而阻碍了C、N原子向基体内的进一步扩渗。

超音速火焰喷涂NiCr-Cr_3C_2涂层的组织结构与摩擦学性能

为进一步提高超音速火焰喷涂NiCr-Cr_3C_2涂层的性能,采用超音速火焰喷涂技术在AISI1045钢基体上制备NiCr-Cr_3C_2涂层。采用扫描电镜、X射线衍射仪分析了涂层的形貌、相结构及化学成分;测试了涂层的显微硬度、弹性模量、结合强度等;采用摩擦磨损试验探究了涂层的摩擦学性能,得出了摩擦系数随时间的变化曲线及涂层的摩擦磨损机理。结果表明:超音速火焰喷涂NiCr-Cr_3C_2涂层晶体结构复杂,含有单晶、纳米晶,还含有少量非晶相,且涂层结构致密,孔隙率低,显微硬度为916 HV3 N,弹性模量为248.671 GPa,结合强度为63 MPa;在不同载荷条件下,涂层的摩擦系数随时间变化趋势大致相同,且载荷越大,摩擦系数越低,磨损体积越大;载荷为20 N时,涂层磨损机制表现为黏着磨损,载荷增大到60 N时,涂层磨损机制过渡到磨粒磨损。

软氮化和化学镀镍双重强化对45钢表面性能的影响

先对45钢表面分别进行化学镀和软氮化处理,然后进行软氮化后再化学镀镍磷试验。测量了3种方法强化后渗(镀)层的厚度、硬度和分别在150N和100N试验压力下渗(镀)层的耐磨性。结果表明,软氮化后再进行化学镀所得的渗(镀)层有较大的厚度、硬度和耐磨性,该复合强化方法是一种有效的表面强化方法,有较好的应用前景。