Die Service Life Research Articles

Influence and application of laser parameters on unit of H13 steel by laser remelting process

Die service life improvement is an important problem in high-pressure die casting industry. Former studies show that biomimetic laser remelting process provides desirable microstructural and microhardness changes, which induces the intensified particles for improving the service life. The present study concerns laser surface remelting of H13 tool steel in a quenched and tempered state using an Nd:YAG laser. This purpose is to obtain data for establishing database of laser parameters for H13 material, which is helpful for applying laser remelting on die casting dies. The influence of laser parameters on the characteristics of the unit has been investigated. The interrelationships among the laser processing parameters, the penetration depth, the width, and the area of the unit were discussed by single-factor experiments. A set of die casting die was selected and processed by laser remelting, and the die service life has been increased from 13,000 shots to 27,000 shots under practical die casting conditions.

Multiobjective Optimization of Precision Forging Process Parameters Based on Response Surface Method

In order to control the precision forging forming quality and improve the service life of die, a multiobjective optimization method for process parameters design was presented by applying Latin hypercube design method and response surface model approach. Meanwhile the deformation homogeneity and material damage of forging parts were proposed for evaluating the forming quality. The forming load of die was proposed for evaluating the service life of die. Then as a case of study, the radial precision forging for a hollow shaft with variable cross section and wall thickness was carried out. The 3D rigid-plastic finite element (FE) model of the hollow shaft radial precision forging was established. The multiobjective optimization forecast model was established by adopting finite element results and response surface methodology. Nondominated sorting genetic algorithm-II (NSGA-II) was adopted to obtain the Pareto-optimal solutions. A compromise solution was selected from the Pareto solutions by using the mapping method. In the finite element study on the forming quality of forging parts and the service life of dies by multiobjective optimization process parameters, the feasibility of the multiobjective optimization method presented by this work was verified.

Optimize Design on the Key Parts of Ring Die Fuel Pellet Machine

This paper analyzes the problems existing in the design and operation of ring die fuel pellet machine, and proposed to optimize the key parts. Determine the reasonable number of roller on the theory of fatigue damage after drawing up the related design parameters of ring die and the roller, a three-dimensional model of the link mold pellet machine is established using Pro/E soft-ware, and transferred the model into ADAMS software through Mech/Pro which dedicated interface software, then used ADAMS to make a dynamics simulation. Through calculation, the stress amplitude impact on the ring die and the Energy consumption per unit output are smallest when roller number is four. So, ring die service life and equipment production efficiency can be improved effectively through setting up reasonable roller number. Keywords-fuel pellet machine; roller; ring die; fatigue damage; three-dimensional model; dynamics simulation

Microstructure and Properties of Hot Working Die Steel H13MOD

Compared with H13 steel, the influences of different heat treatment process on the microstructure and properties of the new type of hot working die steel H13MOD were studied. The results show that the complete austenitizing temperature of H13MOD is around 1030 °C and the quenching hardness achieves the maximum value at this temperature. While for H13, the complete austenitizing temperature is above 1100 °C and the quenching hardness rise constantly with the quenching temperature increasing. In quenching process, the undissolved MC carbides can prevent the coarsening of grain in both steels. With the rise of quenching temperature, when MC carbides dissolve completely, the grain grows quickly. The hardness and strength of H13MOD at higher tempering temperature (above 570 °C) are nearly the same as those of H13, but its toughness is higher than that of H13. Mo2 C carbide is the main strengthening phase in H13MOD, which is attributed to the higher content of Mo. The quantity of VC eutectic carbides is reduced because of lower content of V in H13MOD, which plays an important role in enhancing the impact toughness of H13MOD. Under a certain strength condition, H13MOD steel can be used in the environment that higher toughness is required and the service life of die casting mold can be improved.

Method for improvement of die-casting die: combination use of CAE and biomimetic laser process

Die service life improvement is an important problem in high-pressure die-casting industry. Die service life, which is defined as the maximum product number produced before it fails, and die performance directly determine the production cost and quality of die-casting product. To reduce the repair and maintenance costs, an approach to prevent die from thermal damage and prolong the die lifetime is required. Biomimetic laser-remelting process (BLRP) provides a promising method to improve the service life of die-casting mold. However, the laser processing regions can only be determined by experiences. In order to determine the exact laser processing regions for a set of new die before BLRP, a combination system of CAE and BLRP is proposed in this paper. Through analyzing the mold filling process and the temperature distribution, potential thermal cracks are worked out by numerical simulation system, which are the laser processing regions. The method proposed in this paper advances the efficiency of the BLRP. And practical production validates the veracity and the reliability of the method.

Finite element simulation of the effect of Al‐6063 billet quality on the extrusion die performance

PurposeIt has been observed from the history of failed dies used in local extrusion industry that after certain press cycles, severe die damage occurs by using more number of in‐house recycled billets. The purpose of this paper is to focus on the effect of billet quality on the extrusion die service life, based on using microstructural and finite element analyses.Design/methodology/approachNumerical solution of stress distribution in extrusion die using microstructural and finite element analyses.FindingsSimulation results demonstrate that extrusion die experiences high stresses and strains at critical locations by running secondary billets. Billet deformation behavior also shows that secondary billet has more resistance to flow during extrusion cycle, which results in such high stresses and strains in the die.Research limitations/implicationsThe study includes a particular die used to extrude the aluminum alloy billets. It may need to generalized including materials other than aluminum alloy.Practical implicationsThe findings are original and believed to be useful for engineers working in the extrusion dies. Since it is shown that secondary billets (recycled billets) have more resistance to flow in the dye, a care should be taken when estimating the die life for the practical applications.Originality/valueIt is an original work. It deals with the comparison of new and recycled billets's performance in terms of stress formation in the die during the extrusion cycle.

The Effect of Heat Treatment Atmosphere on Hardening of Surface Region of H13 Tool Steel

The main objective of the die heat treatment is to enhance the surface hardness and wear properties to extend the die service life. In this paper, a series of heat treatment experiments were conducted under different atmospheric conditions and length of treatment. Four austenitization atmospheric conditions were studied and although each heat treatment condition resulted in a different hardness profile, it did not affect the results for gas nitriding. All samples subjected to the nitriding process produced similar thicknesses of hardened case layer with average hardness of 70 - 72 HRC if the initial carbon content is not too low. It was shown that heat treatment without atmospheric control results in a lower hardness on the surface since the material was subjected to decarburization effect. The stainless steel foil wrapping around the sample and heat treatment in a vacuum furnace could restrict the decarburization process, while pack carburization heat treatment resulted in a carburization effect on the material.

Die-Casting Die Design Based on the Application of CAE Simulation

High pressure die casting is a high volume component manufacturing process which is used extensively in many aspects. There are many factors affecting the quality of die-casting die. In this paper, the CAE simulations of filling and solidification processes for die-casting are studied. Numerical analyses are presented for two practical die-casting parts using HZ CAE software. The temperature distributions and filling states in solidification and filling process are presented. Then the deficiencies of the part are predicted. Based on the analyzing results, the structures of the two dies are optimized and longer die service life and high-quality castings are obtained. It is proved that CAE simulation results can offer a helpful reference for die-casting die design.

Cover die service life improvement by biomimetic laser-remelting process and CAE simulation

Die service life improvement is an important problem in high-pressure die-casting industry. As many factors affecting the service life, die service life improvement is a systematic project. In this paper, a cover die-casting die was investigated in order to increase its life time. Different die materials, computer-aided engineering (CAE) analysis, biomimetic laser-remelting process, and die structure optimization are adopted in order to enhance its performance. The die service lives are traced for dies of different die materials (H13 and SKD61). The die service lives are compared for dies with/without structure optimization with the help of CAE simulation. The application shows that CAE simulation is a useful tool for die structure optimization. Experiment result on SKD61 die steel after laser-remelting process shows that biomimetic laser-remelting process provides desirable microstructural and microhardness changes in biomimetic units, which induces the intensified particles for improving the service life.

Prediction of damage zone in hot forging die and suggesting proper heat treatment for improving die service life

In the present research, using MSC Super Forge simulation software and analysis of stress, strain, contact pressure, and temperature distribution in different points of hot forging operation of a work piece and also by considering the interaction between the work piece and die, the zones of die which are prone to early failure and damage have been predicted. The results of simulation have been compared with experimental results of die service. Simulation outputs show a good agreement with practical conditions. In the next step, after studying the effect of heat treatment on the die performance, a proper heat treatment procedure is introduced to improve die service life. Finally, capability of this solution to overcome die damages would be verified with practical behavior of dies.

Laser Bionic Strengthening Local Grid of Mould Surface

For the short life of enterprise hot work die directly caused to problems in the waste of resources and the rising cost of production. Based on studying the biological prototype of crack-resistance of dragonfly wings and finding surface thermal fatigue crack is one of the main factors affecting life of the hot work mould, it is put forward thoughts about the local laser bionic strengthening the grid mould surface. Different from the traditional mould surface integral laser transformation hardening (LTH) technology, by using laser melting simulating dragonfly wings to block localized crack in the partial surface of mold, bionic strengthened die life is improved within 1~1.5 times. Experiment results on die steel shows that it is provided a new method to improve the service life of die casting mold and promoting this technology will bring significant economic benefits for the mold industry.

Study on the Rules and Effects of Wear on Die Service Life in Steel Synchronizer Gear Ring Forging Process

The die accuracy and die service life reduce due to die wear during precision forming processes of steel synchronizer gear ring. The most serious part of wear is the middle between two tooth shapes. The rules of the wear and initial die hardness and frictional coefficient are analyzed based on numerical simulation. It shows that the higher of the initial die hardness, the better antiwear and good lubrication is benefit to reduce wear and prolong the die service life. The effect of the temperature on die life is reflected through hardness. The relationship of die hardness and die temperature, forming time is deduced. The higher of the die temperature and the longer of the forging time, the more serious of die wear. To prolong the die life and improve the quality of forgings, the synthetic forming technology is adopted and the ejection way and control system of the Plate Friction Press are improved. Experiment verification shows that the die service life has been prolonged.

Performance enhancements of high-pressure die-casting die processed by biomimetic laser-remelting process

Die service life improvement is an important problem in high-pressure die-casting industry. Experiment results on die steel shows that biomimetic laser-remelting process provides a promising method to improve the service life of die-casting die. A casting with uneven wall thickness was selected and problems existing in die-casting production were analyzed. The corresponding die-casting die was processed by biomimetic laser-remelting process. The application result indicates that the service life of the die processed by biomimetic laser-remelting process has been increased from 12,000 to 28,000 shots, which is more than twice that of no processed one under real high-pressure die-casting conditions. The application of laser-remelting process provides desirable micro-structural changes in biomimetic units, which induces the intensified particles effect for improving the service life.

The performance of thermally sprayed titanium based composite coatings in molten aluminium

The service life of die and tool steels in contact with molten aluminium is important in the aluminium processing industry. This article describes an investigation of the efficiency of thermally sprayed Ti(Al,O)/Al 2O 3 and TiAl(O)/Al 2O 3 composite coatings in resisting aluminium soldering on H13 tool steel. The powder feedstocks for making the composite coatings were produced by high energy mechanical milling of a mixture of Al and TiO 2 powders using different molar ratios followed by a thermal reaction process. The feedstocks were then thermally sprayed using a high velocity oxygen fuel (HVOF) technique onto an H13 steel substrate to produce composite coatings. The performance of the coatings was assessed in terms of Al soldering and liquid metal corrosion resistance after immersing in molten aluminium at a temperature of 700 ± 10 °C. The results of this study showed that composite coatings have a potential to act as a physical barrier to prevent aluminium attack on H13 tool steel. The nature of Al attack on H13 tool steel changed from generalised to more localised attack with the thermally sprayed coating. A Ti(Al,O)/Al 2O 3 composite coating was not attacked by molten aluminium, however localised attack on a H13 tool steel substrate was found to be caused by molten metal penetration through defects in the coating. Composite coating TiAl(O)/Al 2O 3 was attacked by molten aluminium resulting in dissolution of the coating. Composite coatings showed significantly lower dissolution in molten aluminium compared with the uncoated H13 steel. A Ti(Al,O)/Al 2O 3 composite coating was found to be a more effective protective coating than a TiAl(O)/Al 2O 3 composite coating due its greater resistance to molten aluminium attack.

Numerical Simulation on Two-Step Isothermal Glass Lens Molding

Glass lens molding is an effective approach to produce precision micro aspheric glass lens at high efficiency. In this paper, a new two-step isothermal glass molding process was proposed. The mechanisms of new molding process were analyzed. Finite element simulation was conducted to analyze the key factors such as the pressing load, die damage, molding time and residual stress of lens during the traditional molding and the two-step isothermal molding. The results showed that the two-step isothermal glass lens molding process may decrease residual stress and improve stress and strain distribution. Furthermore, prolong the service life of die.

Fatigue Life Prediction of Isothermal Forging Dies Based on Average Strain Method

Isothermal forging die plays an increasing important role in plastic forming. During isothermal forging process, die bears high and long-time thermomechanical loading, which leads to short service life and poor reliability. Therefore, estimating isothermal forging die life using traditional method will engender great errors. In this paper, an average strain of fatigue process zone in danger region is introduced to estimate service lifetime of isothermal forging die. An upper die of a Ti-4Al-6V disc is analyzed to investigate the service life of die. The result shows that using average strain method can estimate service life of isothermal forging die more exactly.

Influence of Billet Quality on Hot Extrusion Die Life and its Relationship with Process Parameters

Apart from other factors such as die design and manufacturing, heat treatment, working conditions etc, performance of hot extrusion die can directly be related to the billet quality used in the extrusion press. The purpose of this paper is to investigate the effect of Al-6063 billet source (primary or secondary) on extrusion die life based on microstructural and statistical analyses. In microstructural investigation, secondary (remelt) billet cast in-house at local extrusion plant is compared with primary (smelter) billet by applying different material characterization techniques including optical microscopy, hardness measurement, X-ray diffraction (XRD) analysis, and energy dispersive spectroscopy (EDS). The statistical study is based on the failure history of some 53 hollow-profile dies in which the effect of billet quality on various measurable process parameters including extrusion ratio, billet temperature, exit temperature and repeated nitriding is analysed and related with useful die service life. Comparatively coarse grain structure, non-homogeneous distribution of secondary phases, and high hardness in the case of secondary billet were found responsible for poor die performance as observed in statistical investigation of failed dies. Two types of regression models are also proposed for prediction of die life in terms of secondary billets’ usage and measurable influencing parameters. Using current results, some suggestions during in-house billet preparation of secondary billets have been devised for improved die life.

Performance of Al-6063 Primary and Secondary Billets Used in Hot Aluminum Extrusion

The service life of tooling plays an important part in the economics of the extrusion process. A number of causes are considered responsible for initiating damage to the dies before its designated life is reached. Apart from other factors such as die design and manufacturing, heat treatment, working conditions, etc, the performance of the die can directly be related to the billet quality used in the extrusion press. The purpose of this paper is to investigate the effect of Al-6063 billet source (primary or secondary) on extrusion die failure, based on microstructural investigation. A secondary (remelt) billet cast in-house at a local extrusion plant is compared with a primary (smelter) billet by applying different material characterization techniques, including optical microscopy, Vickers microhardness measurement, X-ray diffraction (XRD) analysis, and energy dispersive spectroscopy (EDS). It is observed that a secondary billet has a comparatively coarse grain structure, nonhomogeneous distribution of secondary phases, inclusions, and high hardness that can be associated with poor casting and homogenization practice. In view of present results, some suggestions during in-house billet preparation of secondary billets have been formulated for improved die service life.

Effect of Al-6063 Billet Quality on the Service Life of Hot Extrusion Die: Metallurgical and Statistical Investigation

The current paper presents results about the effect of Al-6063 billet quality on the service life of AISI-H13 hot extrusion dies based on microstructural and statistical investigation. In the first half of the paper, secondary (remelt) billet cast in-house at local extrusion plant is compared with two sources of primary (smelter) billet by applying different material characterization techniques including optical microscopy, hardness measurement, x-ray diffraction (XRD) analysis, and energy-dispersive spectroscopy (EDS). The second half of the paper evaluates the performance of primary and secondary billet types based on statistical analysis of data collected on 53 hollow-profile dies from a local commercial extrusion setup. It was observed that the secondary billet has a comparatively coarse grain structure, nonhomogeneous distribution of secondary phases, and high hardness that can be associated with poor casting and homogenization practice. Statistical analysis covers overall analysis of collected data followed by detailed study of percentagewise use of billet quality in terms of die profile complexity/extrusion ratio. Analysis has shown that dies extruding a high percentage of secondary billets are more susceptible to early die failure on overall basis. For more complex dies with high extrusion ratio, average die life further reduces with increased percentage of secondary billet usage. Regression models are also proposed for prediction of die life in terms of secondary billet usage and extrusion ratio. Considering results of present microstructural and statistical analysis, some suggestions during in-house billet preparation of secondary billets have been formulated to prevent early die failure.

Die fatigue life improvement through the rational design of metal-forming system

In metal-forming industries, die is an important tool for fabrication of metal-formed products. Die service life, which is defined as the maximum product number produced by die before it fails, and die performance directly determine the quality of metal-formed product and production cost. In cold forming process, die service life basically refers to the die fatigue life. The die fatigue life is determined by the design of metal-formed product and die, forming process configuration, die stress and the entire metal-forming system. In this paper, a methodology for optimization of die fatigue life is developed via the rational design of metal-forming system in such a way that the die stress is optimal and further the die design in terms of its service life is the best. To realize this thought, the S– N approach is employed for evaluation of die fatigue life. The die stress is first identified via the integrated simulation of billet plastic flow and the die deformation during the forming process. The die stress is then optimized via the rational design of the combination of metal-formed product, die and process configuration. The optimal die life is thus determined. Furthermore, a framework for implementation of this methodology is developed and case studies are used for verification and validation of the developed methodology.