Scaling laws for the laser-oxygen cutting of thick-sheet mild steel

The laws of scaling the laser-oxygen cutting of mild steel based on experimental optimization are proposed. The sheets from 5 to 25 mm are cut with the aid of CO₂ laser.It has been established that the minimal surface roughness is reached within the whole thickness range if the laser energy value per unit of the removed material and the power per sheet thickness unit are held constant. The results permit to determine the laser power and cutting speed values optimal for a certain sheet thickness. Within the range of large thicknesses, the conditions of cutting with minimal roughness are written as ratios between dimensionless variables. Evaluation of the maximum thickness of the sheet, at which the high-quality cutting is realizable, has been made.     

An analytical model for the optimized design of micro-textured cutting tools

Proper design of micro-textured cutting tools is an effective strategy to improve the machining performance by reducing the tool-chip contact length and the resultant friction and thus improving tool life and workpiece surface integrity. In this paper, an Oxely-based analytical model is developed to optimize micro-textured cutting tool design(s) which eliminate the occurrence of derivative cutting. The model accommodates any workpiece material, tool geometry, and machining parameter. The model was validated by orthogonal cutting of AISI 1045 steel tubes. The results show that the optimum micro-texture design eliminates derivative cutting and lowers forces compared to the non-textured cutting tool.     

A model for mild steel oxidation in CO2

A model for the oxidation of mild steel in CO₂ is proposed, which is an extension of the ideas of Bruckman, Romanski, and Mrowec. A single layer of magnetite forms initially by short-circuit solid-state transport of cations. Lattice vacancies are injected into the underlying metal and eventually cause loss of scale-metal adhesion in some areas. Microchannels develop in the overlying oxide and the scale continues to grow at both oxide-metal and oxide-gas interfaces. In this duplex stage of growth, inner layer oxide nodules form in the vacancy condensation volume produced by departing metal. Their growth is restricted by a build-up of CO released by the oxidation reaction, so that a microporous structure is perpetuated. Breakaway oxidation is the result of local destruction of CO when a catalyst for the Boudouard reaction eventually forms. The inner layer crystals then grow in an atmosphere of higher oxygen potential, and deposited carbon produces a very porous structure.     

A study of micropool lubricated cutting tool in machining of mild steel

This paper presents an experimental study of the performance of micropool lubricated cutting tool in machining mild steel. Microholes are made using femtosecond laser on the rake face of uncoated tungsten carbide (WC) cutting inserts. Finite element analysis is conducted to assess the effect of microholes on the mechanical integrity of the cutting inserts. Liquid (oil) and solid (tungsten disulfide) lubricants are used to fill the microholes to form micropools. A comparative study is conducted between micropool lubricated (surface-textured) cutting tools and dry/flood-cooled conventional (untextured) cutting tools. Three cutting force components are measured and compared. Tool–chip contact length and chip morphology are examined using optical microscope. It is found that the mean cutting forces (F_f, F_t, and F_c) are reduced by 10–30% with micropool lubrication. The chip–tool contact length is reduced by about 30%. Coiling chips are produced with micropool lubricated cutting tool while long and straight chips are formed with the conventional cutting tool. Liquid and solid lubricants are found to be equally effective in reducing the contact length and coefficient of friction at the chip–tool interface. There is no adverse effect on the performance of the insert with microholes on the rake face.     

套裁排样在数控切割优化过程中的应用

板材下料问题是许多机械加工企业的实际问题,受加工车间生产模式、管理水平、人员素质、工艺手段等诸多因素限制,手工设计套裁方案不能对全局统筹把握.而套裁排样软件作为一种辅助工具,利用其特有的数据库系统,经过复杂运算,能够准确地辅助工程技术人员从复杂的工作中解脱出来,并使材料达到合理利用,以降低原材料的制造成本.     

薄壁低碳钢管焊接变形的数值模拟

基于泛用软件ABAQUS,开发了适用于模拟熔化焊产生的温度场、应力场和应变场的热弹塑性非线性有限元计算方法.通过建立三维有限元模型和采用双椭球高斯体积移动热源,对低碳钢薄壁钢管的焊接温度场和焊接变形进行了数值模拟.同时还采用焊接机器人实际进行了低碳钢薄壁钢管的焊接,并实测了钢管的焊接变形.结果表明.数值模拟得到的变形和...     

SKD11铣削刀具寿命试验研究及工艺参数优化

为提高SKD11模具钢铣削刀具的寿命,对SKD11模具钢进行了刀具寿命铣削试验,基于极差方法分析了各工艺参数对刀具寿命的影响规律。基于刀具寿命铣削试验,利用多元线性回归方法,推导并求解出了SKD11模具钢铣削刀具磨损的数学模型。利用最优化设计方法和MATLAB优化工具箱,以加工效率和刀具磨损为目标函数,针对实际的铣削问题优选了工艺参数。优化的工艺参数能兼顾刀具寿命和加工效率,为加工企业降低综合生产成本提供了重要的理论依据和案例参考。     

Development of micro milling force model and cutting parameter optimization

Taking the minimum chip thickness effect,cutter deflection,and spindle run-out into account,a micro milling force model and a method to determine the optimal micro milling parameters were developed.The micro milling force model was derived as a function of the cutting coefficients and the instantaneous projected cutting area that was determined based on the machining parameters and the rotation trajectory of the cutter edges.When an allowable micro cutter deflection is defined,the maximum allowable cutting force can be determined.The optimal machining parameters can then be computed based on the cutting force model for better machining efficiency and accuracy.To verify the proposed cutting force model and the method to determine the optimal cutting parameters,micro-milling experiments were conducted,and the results show the feasibility and effectiveness of the model and method.     

High speed TIG–MAG hybrid arc welding of mild steel plate

A TIG–MAG hybrid arc welding process was proposed to achieve high speed welding. The influences of hybrid arc welding parameters on welding speed and weld appearance were studied through orthogonal experiment and the microstructures and mechanical properties of weld were tested and compared with that of the conventional MAG weld. The TIG–MAG hybrid arc welding speed could reach up to 3.5 m/min for bead-on-plate welding of 2.5 mm thick mild steel plate under the condition of high quality of weld appearance and 4.5 m/min for butt welding of 2 mm thick mild steel plate, respectively. The mechanical properties of hybrid arc weld were not lower than that of the conventional MAG weld. The assistant TIG arc could effectively stabilize the MAG welding current and MAG arc voltage in high speed TIG–MAG hybrid arc welding process. The stable hybridization obtained by balance between TIG and MAG welding current and proper wire-electrode distance was a key factor to stabilize the welding process.     

Parameter optimization of dissimilar resistance spot welding on ultra-high strength hot-stamped steel and mild steel by numerical simulation

In this study,a coupled axisymmetric finite element model (FEM) was built to simulate the resistance spot welding (RSW) process between ultra-high strength hotstamped (UHSS) and mild steel by SORPAS software.Via simulating this process,the temperature distribution and dynamic temperature curves of the welding area were studied,and welding spatter phenomena were predicted and validated by comparing them with experimental results.By adjusting the welding parameters in numerical simulation,appropriate welding parameters were achieved.Moreover,the mechanical properties of the welding joints under the optimized conditions were also compared with those of not optimized.The study results have already been applied in a manufacturing production.It can also provide guidance for the RSW on UHSS and mild steel.     

The oxidation dynamics of laser cutting of mild steel and the generation of striations on the cut edge

Over the past two decades CO₂ laser cutting has grown from an obscure laboratory technique into an important branch of manufacturing engineering. The most commonly cut materials are steels and a great deal of industrial and scientific research has been carried out on the laser-material interactions that generate a cut. This paper concentrates on the phenomena which give rise to a cyclic cutting event when a CO₂ laser in conjunction with an oxygen jet is used to cut mild steel. The nature of the cut edge striation produced by the cyclic oxidation reaction is explained thoroughly and a possible oxidation cycle is postulated. It is demonstrated that the key to understanding the cyclic nature of the cutting event is the self-limiting nature of the oxidation of the steel in the cut zone.     

一种激光切割机横梁的优化设计方法

将某型号激光切割机的横梁进行简化,建立横梁结构参数化几何模型,并根据参数化模型建立有限元模型,根据模态分析结果从多个结构参数中选取设计变量,使用有限元分析软件对设计变量进行优化,得到结构参数最优解,此方法可代替传统方法对模型进行反复修改和计算,可提高设计效率。     

Analytical modeling and experimental investigation of tool and workpiece temperatures for interrupted cutting 1045 steel by inverse heat conduction method

Cutting temperature is a key factor which directly affects tool wear, workpiece integrity, and machining precision in high speed machining process. The interrupted cutting process consists of several periodical characteristics, such as cutting force and time varying heat source. Induced cutting temperature models with time varying heat flux are developed in this paper to predict temperature distribution at tool inserts and workpiece during interrupted cutting process. A set of interrupted cutting experimental installation is designed to verify the proposed models. The comparison of predicted and measured results for 1045 steel in interrupted cutting processes shows reasonable agreement. The measured temperature of both the tool inserts and workpiece increase firstly and then decrease as the cutting speed increases. The peak temperature of the workpiece appears at 1500 m/min, while the peak tool inserts temperature appears at 1250 m/min approximately. Heat flux is calculated by the inverse heat conduction method. The applicability of Salomon's hypothesis to the temperature of tool inserts and workpiece is discussed during the interrupted cutting process. The dropped temperature at high cutting speed is mainly caused by that heat flux into tool inserts decreases and heat transfer time is not enough after the critical cutting speed.     

Correlation between corrosion rate and AE signal in an acidic environment for mild steel

The AE method is an effective technique for inspecting corrosion damage of mild steel, such as tank bottom floors. However, the correlation between AE signals and corrosion behaviour for mild steel has not yet been fully clarified. In the present study, the authors considered that the corrosion regions of bottom floors become a strong acid environment by Cl⁻, as reported in a previous study. Thus, the polarization resistance for the test pieces of mild steel was measured with an AC impedance method under a strong acid environment. It was clear that the polarization resistance indicated the corrosion rate for a test piece of mild steel in the experiments. While measuring the AE signals, the corrosion rate was monitored with a test piece. As a result, the AE signal showed good correlation with the corrosion rates of the test pieces. The corrosion behaviour of the test pieces was then discussed with the corrosion potential measured during the experiments. Furthermore, the cathode current was changed to control the generated hydrogen gas volume. The volume of the hydrogen gas generated from the cathode reaction was correlated to the AE signals.     

有机物切割刀具用钢的研究和应用

通过分析有机物切割刀具用钢的使用性能及设计要求,设计并生产了一种新型有机物切削刀具用的高碳低合金钢,采用了粒子相钉扎晶界细化晶粒及低温二次硬化技术,使该钢的硬度可达68～72 HRC,并有一定韧性与之匹配.该钢已经应用在卷烟厂制作解把刀、打叶刀、切丝刀等刀具,以及其他有机物切削刀具,使用性能及寿命均高于同类型钢种.     

高推力辊式电磁搅拌器在电工钢板上的应用及优化

针对某钢厂生产电工钢板项目的实际案例,通过有限元分析与实验测量相结合的方法研究了高推力辊式电磁搅拌器在230 mm铸坯上的最佳搅拌参数、搅拌参数随铸坯厚度变化规律及冶金效果。结果表明,电流为500 A,频率7 Hz,对230 mm铸坯能起到良好的搅拌效果。同设备高推力辊式电磁搅拌器搅拌不同铸坯,为获得较好冶金效果,随铸坯厚度的增加,电流强度和频率分别呈线性增加和逐渐递减趋势进行调整。产品使用后的冶金效果表明:优化应用高推力辊式电磁搅拌器可以明显改善铸坯的凝固组织,提高等轴晶率。     

钢材切割现状及Fast切割软件的应用

现代切割技术有别于传统手工切割技术．它是基于现代计算机信息技术．针对不同的切割下料设备。对传统切割技术加以改进提高，发展成为以优化套料技术、钣金展开技术和数据库管理技术为代表的计算机辅助切割生产和管理软件。以有效提高钢材综合利用率，提高切割效率和切割质量．加强切割生产管理。     

关于钢铁制造流程优化与产品优化问题的讨论

强调在新世纪里中国钢铁企业要注意研究钢铁制造流程的功能,指出制造(生产)流程对钢厂的生存和发展有着广泛的关联度和综合影响力,制造流程的结构优化是钢厂增强市场竞争力和拓展社会经济功能的有效手段。简要地叙述了钢铁制造流程的构成要素是"流"、"流程网络"和"程序"。"流"按一定的"程序"在"流程网络"中动态有序地、准连续地、紧凑地运行,可以实现多目标优化。讨论了中国钢铁企业生产流程优化的现状和发展方向,还就中国钢铁产品优化过程中有关炼钢、轧钢方面的问题进行了总体性探讨。在新世纪前20年,要集中有关资源加速发展薄板及其深加工产品,以实现中国钢铁产品的结构调整,促进钢厂结构的优化。     

A model for prediction of dimensional tolerances of laser cut holes in mild steel thin plates

Dimensional variation in laser cutting of sheet metals depends on two factors: the accuracy and repeatability of the positioning system, and the thermal effects of the laser beam on the workpiece material. In this work, a physical model was formulated to estimate the dimensional accuracy of holes produced with laser cutting. The model included the assumption that the layer adjacent to the hole is plastically deformed and contains residual stresses up to the yield strength. The model was used to calculate the size of the hole and cut-out disk of varying radii in steel plates with thicknesses of 3.2 mm and 6.4 mm. The model-predicted data were verified with the experimental data obtained using a 1 kW continuous wave CO₂ laser. Results indicated that there is an excellent correlation between the model and the experimental data especially for smaller diameter holes.     

A hybrid model combining simulation and optimization in chemical mechanical polishing process

A hybrid model composing of 2D axisymmetric quasic-static finite element method, back-propagation network, and direct complex searching optimization for chemical mechanical polishing process (CMP) was established to investigate the optimal parameter sets under the minimum nonuniformity (NU) on wafer surface. During polishing, the revolutions of the wafer and the pad were assumed to be the same, the force form of carrier was axisymmetric and uniformly distributed, and the minimum potential energy principle and the Hooke's law were considered. Thus, a 2D axisymmetric quasic-static finite element model was developed in which the wafer carrier, carrier film, wafer, and pad were involved. Under the conditions that the carrier load varied from 0.03448 MPa to 0.10345 MPa, the pad's elastic modulus was from 1.1448 MPa to 3.4345 MPa, and the pad's thickness was from 0.6985 mm to 2.0955 mm, a total of 35 sets of finite element simulated results were then used as the database of the back-propagation neural network-learning model. Among them, 27 sets of data were constituted in the training data, and the other 8 sets of data were the test data. Using these datasets, the network-learning model concerning the relationship between the von Mises stress on the wafer surface and the process parameters, including the carrier load, pad's elastic modulus, and thickness of pad, could be established. Finally, direct complex searching optimization was applied to obtain the optimal parameter sets under the minimum NU on the wafer surface. The results showed that under the optimal condition of the carrier's load of 0.052 MPa, pad's elastic modulus of 3.19 MPa and pad's thickness of 0.699 mm, the minimum NU of 1.65995 could be achieved.