挤压筒加热及温度控制问题的探讨

介绍了挤压筒加热方式及各种加热器使用现状,并对挤压筒加热过程中存在的问题进行了分析.分析结果表明,挤压筒加热以应力分布均匀为原则;加热器安装应接近挤压筒中心,尽可能减小外套与内衬之间温差;对挤压筒前、后两端以及顶部和底部应采用独立加热系统,通过多区加热元件正确定位,控制挤压筒温升和温差,可以使挤压筒温度及应力分布均匀,...     

碳化硅真空烧结炉温度场数值模拟与系统优化

为了提高碳化硅真空烧结炉加热系统的加热效率和温度均匀性,以ZSD4.5-1150C真空高温烧结炉为参考建模,采用Ansys Fluent软件、DO辐射模型,模拟了空载状态下真空烧结炉的瞬态温度分布规律,并与实测数据进行对比,最大误差在10%以内。在此基础上,进一步研究加热速率、加热管直径、加热管与有效加热区间距对加热系统温度分布特性及加热效率的影响,并对加热系统进行优化。结果表明,适当增大加热速率和加热管直径,可有效提高加热系统的加热效率和温度均匀性,加热管与有效加热区间距对加热系统性能影响不大;具体优化方案为加热速率9 K/min、加热管直径ø45 mm、加热管与有效加热区间距50 mm,优化后系统加热时间减少了60 min,加热效率提高了30%,温度均匀性满足工艺要求。     

MCU与DSC对感应加热电源的网络化远程监控与实现

针对传统的高频感应加热电源操作安全性差、自动化程度低、难以实现网络化控制等缺点,设计了一种基于微控制器(MCU)和数字信号控制器(DSC)的新型高频感应加热电源网络化远程监控系统.该系统采用RS-485总线和Modbus通信协议,便于组网和改善通用性.介绍了该控制系统的组成和工作原理,给出了软硬件设计.试验证明控制系统实现了高频感应加热电源的网络化远程监控,提高了系统的自动化水平.     

IGBT感应加热/钎焊电源的DSP数字化控制系统设计

用数字信号处理器(DSP)和复杂可编程逻辑器件(CPLD)设计了IGBT感应加热电源控制系统.DSP采用TMS32LF2407A,主要用于实现数字锁相环、参数采样和恒流控制算法;CPLD采用EPM7128,主要用于完成驱动死区时间设置,并由此芯片来完成系统中其它逻辑控制功能.通过这种设计方案,实现了感应加热电源的数字化控制,并给出了相应的软件框图.     

加热面积对球罐局部热处理应力消除效果的影响

针对球罐局部热处理缺少标准支持问题,采用数值模拟方法分析了加热面积大小对焊接残余应力清除效果的影响.结果表明,局部加热过程本身引起的热应力是影响局部热处理效果的控制因素;工程中经常采用的局部热处理工艺,由于加热面积太小,不会取得理想的应力消除效果;增加加热面积可有效提高残余应力消除率,采用足够大的加热面积可达到整体热处理的效果.但局部热处理加热面积的选择会受到球罐体积和壁厚的显著影响,对于相同的残余应力消除率期望值,较大的体积和壁厚均需要采用较大的加热面积.     

挤压筒加热系统优化设计

介绍了挤压筒加热现状,并对典型结构为4个加热区的挤压筒加热系统进行了优化设计,指出挤压筒加热应满足内部热量均衡,采用两组热电偶设计能精确地计算出温度值,每个加热区安装一组防过热加热管可以防止挤压筒过热,达到性能最优.并提出了控制盘箱的合理设计理念,在实际使用中取得了显著的经济效益,提高挤压筒使用寿命.     

铝/钛异种合金激光熔钎焊接头温度分布

以5A06铝合金和TC4钛合金为母材,Alsil2焊丝为填充材料,进行了激光熔钎焊试验.在分析激光填丝熔钎焊传热行为的基础上,建立了3种激光加热模式的热源模型,并采用有限元方法对激光垂直加热、倾斜加热、光束偏置加热以及矩形光斑加热模式下接头温度场进行了计算和分析.结果表明,在铝/钛异种合金的激光熔钎焊过程中,焊缝两侧温度分布严重不对称,将光斑中心向铝合金一侧偏离焊缝中心线0.4～0.6mm可避免钛合金界面局部过热;采用椭圆光斑加热时,加热效果与圆形光斑相近;采用矩形光斑加热,接头界面上下温度分布较为均匀.     

挤压筒分区加热控制系统的设计

介绍了控制系统的硬件配置和软件设计.系统以PLC为控制核心,上位工业控制计算机为人机界面.挤压筒加热分三区控制,采用PLC开关量输出作为全数字三相晶闸管交流调功器的给定,通过调功器输出控制加热功率.通过程序控制、脉冲调宽闭环控制方式,实现了挤压筒温度的梯度加热和恒温控制.     

树脂砂芯热芯盒模具设计

分析了树脂砂芯成形工艺特点,探讨了集装箱角铸钢件砂芯热芯盒模具的加热系统设计、排气系统设计以及模具材料的选择等方面的问题,指出热芯盒模具的加热系统设计及排气系统设计是模具设计的重点。保证加热功率符合要求的情况下,尽量采用多热源均匀加热的效果比较好。采用分型面排气槽、顶杆间隙排气与排气塞排气相结合的排气系统设计能够很好地满足模具排气需要。     

半固态A356合金的瞬态流变行为及半固态压铸研究

采用自行研制的流变装置研究了不同初生相形态半固态A356合金的瞬态流变行为,建立了瞬态流变本构模型;通过设计制造的坯料感应加热系统研究了加热过程中半固态合金的组织演化规律;借助模拟仿真技术确定模具浇注系统和合适的压射条件;对传统压铸机进行改造,生产出高质量的半固态触变成形样件.结果表明,初生相形态和切变机制对半固态合金的瞬态流变行为有显著影响;随合金坯料在液固温区停留时间增加,合金坯料产生组织变化和蠕变,将对后续的成形过程造成影响.     

基于ANSYS的高速精密冲床热-结构耦合分析

基于高速精密冲床的热态特性,对高速精密冲床进行了热源分析与传热机制分析,计算了冲床的热分析的初始条件及边界条件,利用SolidWorks软件建立冲床整机的有限元模型,运用ANSYS软件对冲床进行热-结构耦合分析,求解出该高速冲床处于稳态环境下的整机的温度场和变形场,分析出冲床的加工误差.对比红外热像仪测得的实际冲床温度值,验证了温度场仿真分析结果的可靠性,为冲床的结构优化设计和热平衡设计提供理论依据.     

高速压力机温度场的有限元仿真及实验研究

通过确定高速压力机的运动动力参数,分析计算了高速压力机的热源分布和对流换热系数,并获得了压力机的热边界条件.以有限元方法为基础,建立高速压力机的三维分析模型,进行了温度场变化的分析研究.分析及实验结果表明,所建立的三维压力机温度有限元模型能正确的模拟运行过程中的压力机温度场分布,为压力机热误差分析设计提供了数值分析及实...     

路面铣刨机用聚晶金刚石截齿头的研制

采用纳米结合剂梯度过渡层连接技术,在六面顶压机上合成路面铣刨机用聚晶金刚石截齿头。采用砂轮修整和落锤冲击的方法进行耐磨性、抗冲击性和耐热性等3方面的测试。结果表明:所合成的聚晶金刚石截齿头磨耗比大于25万,抗冲击韧性为1220 J;在750℃保温1.5h的条件下,具有很好的热稳定性;制成的路面铣刨机截齿,在铣刨沥青混凝土路面时,使用寿命是硬质合金截齿的6倍。      

汽车转向节衬套的压装品质控制研究

为了提高汽车转向节衬套压装效率,有必要对影响压装品质的因素进行分析,以获得可用于控制压装工件的曲线规律.通过数据曲线模型提出控制压装过程有3个工件检查阶段,用于检查工件压装的品质.借助PLC设计品质控制系统,控制压装产品的品质.系统通过采集压装过程的数据以及对数据关键值的提取,对压装工件进行品质判别,给出品质判别结果,...     

Improvement of press dies used for the production of diamond composites by means of DUPLEX-PVD-coatings

In the machining of hard materials such as glass or stone, cemented carbides have been recently replaced by diamond tools, consisting of a metallic carrier, on to which diamond segments are brazed. One of the most economic ways for the production of diamond segments is the cold compaction of the mixture of a metallic powder and diamond particles. Due to a highly abrasive sliding contact between diamond particles and the die walls, the wear rate of the press dies is very high. As a result of a low lifetime of the press dies, they must be replaced in short time periods. To avoid the costly and time-consuming substitution of the press dies, in this work PVD-coatings were deposited on the inner surface of the pre-plasma nitrided press dies (DUPLEX treatment). Thereby, various high and low alloy tool steels were treated by means of plasma nitriding process. Subsequently, a nanocomposite TiAlN coating (nc-TiAlN) was deposited by means of a high ionization magnetron sputtering device on nitrided and non-nitrided steel substrates. The mechanical and tribological properties of these coating systems were studied by means of several standard tests such as nanoindentation, ball-on-disc and scratch test. The most wear resistant coating system was chosen to employ on the inner surface of the press dies. The wear resistance of the press dies developed in this study was tested under real loading condition during compaction of the mixture of diamond particles and cobalt powder. It was revealed that employing plasma nitrided tool, steels coated with nanocomposite TiAlN decreases the wear rate of the press dies up to 76%.     

基于三维有限元的六面顶顶锤应力分析

采用三维有限元热力耦合分析方法,综合考虑合成压力、径向预紧力和热应力的影响,对六面顶硬质合金顶锤进行了应力分析,阐述了破坏机理,分析了主要结构参数(顶锤直径、高度)以及径向预紧力对主应力最大值的影响规律,提出了进一步优化参数的思路.     

Effect of nano‐particulate sol–gel coatings on the oxidation resistance of high‐strength steel alloys during the press‐hardening process

The need for lighter constructional materials in automotive industries has increased the use of high‐strength steel alloys. To enhance passenger's safety press hardening may be applied to steel parts. However, as the steel parts are heated up to 950 °C during this process they have to be protected by some kind of coating against the intense oxide formation usually taking place. As the coating systems used so far all have certain disadvantages in this work the ability of nano‐particulate thin coatings obtained by the sol–gel process to improve the oxidation resistance of 22MnB5 steel is investigated. The coatings obtained from three sols containing lithium aluminum silicate and potassium aluminum silicate showed the best performance against oxidation. The structural properties of the coating materials were characterized using different methods like XRD and differential thermal analysis. Comparison of the oxidation rate constants proved the ability of the coatings to protect against oxidation at temperatures up to 800 °C. Press‐hardening experiments in combination with investigations on the thermal shock resistance of the coated samples also showed the ability of the coatings to stay intact during press hardening with only slight spalling of the coatings in the bending areas. The absence of any secondary intermetallic phases and layer residues during laser beam welding experiments on coated samples proves the suitability of the nano‐particulate coatings for further industrial processing.     

50000kN液压机主油缸柱塞热喷涂修复法

详细论述了热喷涂的原理和施工方法。利用热喷涂方法,对50000kN液压机损坏严重的主油缸柱塞实施修复,获得非常优良的表面质量。为快速、高效、低成本设备维修提供了借鉴案例。     

Modelling of compacted graphite cast iron solidification-Discussion of microstructure parameters

A melt maintained for hours in a press pour unit allowed the following changes over time from spheroidal graphite to compacted graphite iron by casting thermal cups at regular time intervals.This provided extensive experimental information for checking the possibility of simulating solidification of compacted graphite irons by means of a microstructure modelling approach.During solidification,compacted graphite develops very much as lamellar graphite but with much less branching.On this basis,a simulation of the thermal analysis records was developed which considers solidification proceeding in a pseudo binary Fe-C system.The simulated curves were compared with the experimental ones obtained from three representative alloys that cover the whole microstructure change during the holding of the melt.The most relevant result is that the parameter describing branching capability of graphite is the most important for reproducing the minimum eutectic temperature and the recalescence which are so characteristic of the solidification of compacted graphite cast irons.     

Evolution of microstructure and texture of AZ61 Mg alloy during net-shape pressing of extruded perform

The micro orientation theological behavior of AZ61 Mg alloy during net-shape forming of tensile specimens via close-die pressing of extruded preformed and the effect of the press deformation rate on the microstructure characteristics were characterized with electron back-scattering diffraction (EBSD) orientation imaging microscopy and metallography. The results indicate that the intensity distribution of basal {0001}<10(1)0 > texture on the cross-section of the extruded perform is uniform and parallel to the extrusion direction. Subjected to pressing in extrusion direction, deformation shear stress leads to grain rotation and basal texture {0001}<10(1)0> deviation from the extrusion direction, spreading in the direction perpendicular to pressing direction. The texture intensity increases with the press deformation rate and reaches its peak value at 50%, which is considerably lower than the value reached in extrusion deformation. Then, the texture intensity decreases with the press deformation rate reversely.