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Impact of Forging Conditions on Plasma Nitrided Hot-forging Dies and Punches  [cached]
Ravindra Kumar,Ram Prakash,J. Alphonsa,Jalaj Jain
Journal of Materials Science Research , 2012, DOI: 10.5539/jmsr.v1n4p11
Abstract: In this work an effort has been made to study the effect on the performance of the plasma nitrided AISI H13 hot-forging dies and punches in two different forging service conditions –namely, fully-automatic and semi-automatic processes. The plasma nitriding is performed to increase the surface properties like –wear resistance and surface hardness of these components. After plasma nitriding the surface hardness of these materials has increased typically from ~500 HV0.01 to ~1200 HV0.01. In the plasma nitriding process high-voltage electrical energy is used to form plasma through which nitrogen ions are accelerated to impinge on the workpiece. The ion bombardment heats the workpiece, cleans the surface, and provides active nitrogen to make iron-nitride compounds. The iron-nitride compounds then diffuse to the workspace to harden the surface. In these two service conditions the plasma nitrided hot-forging dies and punches have shown typically 2.5 to 4 times increment during the performance. It is observed that the increment in the performance of the dies and punches depends on the forging service conditions, i.e., temperature of the dies and punches, shot repetition time and effective cooling of dies and punches in service conditions. Four times increment in the performance of dies and punches is found in the semi-automatic process, whereas two and half times increment in performance of dies and punches is observed in the fully-automatic process.
Deposition and characterization of duplex treated coating system applied on hot work steel AISI H13 Deposición y caracterización de un sistema de recubrimiento duplex aplicado sobre acero para trabajo en caliente AISI H13
Gilberto Bejarano Gaitan,Maryory Gomez Botero,Mauricio Arroyave Franco
Revista Latinoamericana de Metalurgia y Materiales , 2012,
Abstract: AISI H13 steel is widely used for extrusion moulds and other hot work tools fabrication, due to its high toughness, strength and hardness around 56 HRC (Rockwell C). However, this steel possesses a relatively low wear resistance, which reduces its life time under high loading conditions. The aim of this work was to enhance the wear resistance of the steel H13 using the following surface treatments: austenitizing + quenching + tempering (further called “tempering”), tempering and bath nitriding, tempering and coated with chromium nitride (CrN), tempering + bath nitriding + coated with CrN (further called “Duplex coating”). The properties of the treated samples were compared with each other in dependence of the made surface treatment. The coatings were deposited using the r.f. balanced magnetron sputtering deposition technique. The total thickness of the coatings was maintained at 5 μm, while the thickness of the nitrided zone was approximately 140 μm. The microstructure and the crystalline phase composition were investigated by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) technique, respectively. The hardness and the adhesion of the coatings were determined by micro indentation measurements and the Rockwell indentation test, respectively. The wear resistance of the coatings was evaluated using ball on disc tests. The duplex treated samples presented a hardness three order of magnitude higher and showed a wear rate six times smaller than those samples only tempered. El acero AISI H13 es ampliamente utilizado en la fabricación de moldes de extrusión y de otras herramientas para el conformado en caliente debido a su tenacidad, elevada resistencia mecánica, y dureza de aproximadamente 56 HRC (Rockwell C). Sin embargo, este acero posee una relativa baja resistencia al desgaste, que reduce su vida útil cuando es sometido a esfuerzos elevados. El propósito de este trabajo consistió en mejorar la resistencia al desgaste del acero H13 mediante los siguientes tratamientos superficiales: austenización + temple + revenido (denominado en adelante “revenido”), revenido y nitruración líquida, revenido y recubrimiento de nitruro de cromo (CrN), revenido + nitruración líquida + recubrimiento de CrN (denominado en adelante “recubrimiento Duplex”). Las propiedades de las muestras tratadas fueron comparadas en función del tipo de tratamiento superficial realizado. Todos los recubrimientos se depositaron por la pulverización catódica reactiva r.f. y asistida por un campo magnético balanceado. El espesor promedio de los recubrimientos fue de 5 micras, mientr

LUO Chengping,ZHAO Fang South China University of Technology,Guangzhou,

金属学报 , 1990,
Abstract: 应用TEM研究了H13钢580℃软氮化扩散层中同时生成的三种合金氮化物即CrN,VN和Mo_2N的形貌、位向关系及惯习面,发现它们由混合偏聚区经有序化连续转变而成,并且其形貌和晶体学特征与由不变线应变模型所预测的一致。
LUO Chengping ZHAO Fang South China University of Technology,Guangzhou,China,

金属学报(英文版) , 1991,
Abstract: A TEM investigation was made on the morphology,orientation relationship and habit plane ofthree alloy nitrides,namely CrN,VN and Mo_2N simultaneously formed within thediffussional nitrided layers in an H13 steel nitrided at 580℃.It was.found that the nitrideswere precipitated by continuous clustering and subsequent ordering of both interstitial(N)andsubstitutional(Cr,V,Mo)solutes on {001} habit plane,and that the observed morphologyand crystallography of the nitrides were in good agreement with the predictions from theinvariant line stain model proposed for precipitation transformations.
Precise formation the phase composition and the thickness of nitrided layers  [PDF]
J. Ratajski,R. Olik,T. Suszko,J. Dobrodziej
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The article presents the application of the duplex technology (nitriding plus PVD) to modification of the surface of pressure casting dies made of steel WCL (EN: X37CrMoV51). In this technology, there are clearly defined expectations regarding the properties of the surface layer of the dies obtained in the nitriding process. The main part of the article is presentation a complex system of designing, in-situ visualization and control of the gas nitriding process.Design/methodology/approach: In the conception of computer designing, analytical mathematical models and artificial intelligence methods were used.Findings: As a result, possibilities were obtained of the poly-optimization and poly-parametric simulations of the course of the process combined with a visualization of the value changes of the process parameters in the function of time, as well as possibilities to predict the properties of nitrided layers.Practical implications: Computer procedures make it possible to combine, in the duration of the process, the registered voltage and time runs with the models of the process.Originality/value: For in-situ visualization of the growth of the nitrided layer, computer procedures were developed which make use of the results of the correlations of direct and differential voltage and time runs of the process result sensor (magnetic sensor), with the proper layer growth stage.
Comparative analysis of wear mechanism of different types of forging dies  [PDF]
A. Mazurkiewicz,J. Smolik
Archives of Materials Science and Engineering , 2011,
Abstract: Purpose: Hot working dies are influenced by three main factors causing their destruction: the cyclically changeable mechanical loads, intensive thermal shocks, as well as intensive friction, and erosion. The great variety of the shapes of forgings, the material they are made of (carbon steel, alloy steel, brass) and the precision of their production – whether they are supposed to undergo further treatment or are considered to be the final products – result in a variety of problems encountered in the production process. In this paper the wear mechanisms of different types of forging dies, covered by the composite layer “nitride layer / PVD coating” were analysed.Design/methodology/approach: In order to estimate the influence of the different shapes of forgings for their wear mechanism, it was decided to that maintenance tests on two series of tools with different shapes made of DIN 1.2344 steel, coated with composite layer “nitrided layer/CrN coating” needed to be taken. The first one was designed for production of gears pre-forging and the second one was designed for the production of steel synchronizer rings.Findings: The abrasive wear together with thermal-mechanical fatigue and plastic strain is a crucial factor of the process of wearing of forging dies for the production of forgings with high dimensional accuracy and not subject to further mechanical treatment. The variety of the shapes of the forging and the precision with which it is made have strong influence on the intensity of the abrasive wear of forging dies.Research limitations/implications: To ensure higher effectiveness of the application of hybrid technologies of surface treatment for the increase of the durability of forging dies, the complex analysis of the influence of such various aspects of the forging process as: surface treatment, the shape of the die and the cooling and lubricating system are necessary on the development of a new generation of dies with increased operational durability.Practical implications: The obtained results of the tests have been practically applied in the FA “Swarz dz” enterprise to increase the durability of the forging dies for steel synchronizer rings.Originality/value: In order to ensure a required level of effectiveness of the use of layered composites of the “nitrided layer/ PVD coating” type for the increase in the durability of forging dies, it is necessary to properly select the composites on the basis of the analysis of the intensity of forging dies wear mechanisms.
Sensitivity analysis in life prediction of extrusion dies  [PDF]
S.Z. Qamar,T. Pervez,R.A. Siddiqui,A. K. Sheikh
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: Building up on the fracture mechanics (Paris law for crack propagation) based fatigue life prediction model developed earlier by the authors, Monte Carlo simulation has been performed to evaluate sensitivity of die life related to important geometrical and material parameters. Stochastic nature of various fatigue-related die parameters is used to reflect their variability.Design/methodology/approach: Life of the die is one of the most important factors affecting productivity and profitability in hot extrusion of metals. It has been reported in earlier works by the authors that extrusion dies most often fail by fatigue fracture. Experimental studies have shown that cracks preexist in dies due to various factors including heat treatment, machining, and surface hardening. High levels of repeated mechanical and thermal loads result in crack propagation leading to ultimate fracture failure.Findings: Findings of the sensitivity analysis are that fracture life of an extrusion die is very sensitive to initial crack size, section thickness, profile outer diameter and billet length; moderately sensitive to Paris constant and extrusion ratio; and only slightly sensitive to fracture toughness and ram speed.Practical implications: The study can be of direct utility in extrusion die design improvement, formulation of an optimum die replacement strategy, etc.Originality/value: The paper provides basis for a deeper understanding of the factors responsible for fracture failure of an extrusion die exposed to thermo-mechanical fatigue environment.
Investigation of the influence of hybrid layers on the life time of hot forging dies  [PDF]
S. Legutko,A. Meller,M. Gajek
Metalurgija , 2013,
Abstract: The paper deals with the issues related in the process of drop forging with special attention paid to the durability of forging tools. It presents the results of industrial investigation of the influence of hybrid layers on hot forging dies. The effectiveness of hybrid layers type nitrided layer/PVD coating applied for extending the life of forging tools whose working surfaces are exposed to such complex exploitation conditions as, among others, cyclically varying high thermal and mechanical loads, as well as intensive abrasion at raised temperature. The examination has been performed on a set of forging tools made of Unimax steel and intended for forging steel rings of gear box synchronizer in the factory FAS in Swarzedz (Poland).
Study on the microstructure and mechanical properties of medium carbon Cr-Si-Mn-Mo-V steel for cast inserted dies  [PDF]
LIU Jin-hai,LI Guo-lu,HAO Xiao-yan
China Foundry , 2005,
Abstract: The microstructure and mechanical properties of cast inserted dies for automobile covering components were studied. The results show that the as-cast microstructures of cast inserted dies are composed of pearlite, martensite,bainite, and austenite; and that the annealed microstructure is granular pearlite. The mechanical properties of cast inserted dies approach that of forged inserted dies. The tensile strength is 855 MPa, the elongation is 16%, the impact toughness is 177 J/cm2, and the hardness after annealing and quenching are HRC 19 and HRC 60-62. In addition, the cast inserted dies have good hardenability. The depth of the hardening zone and the hardness after flame quenching satisfy the operating requirements. The cast inserted dies could completely replace the forged inserted dies for making the dies of automobile covering components.
Cold Extrusion of Carbon Electrodes Using Dies of CRHS Concept and Performance Analysis  [cached]
Sami Abulnoun Ajeel,Ahmed M. Saleem,Farhad B. Bahaideen,M. Abdul Mujeebu
Modern Applied Science , 2009, DOI: 10.5539/mas.v3n3p44
Abstract: In this article cold extrution of carbon electrodes using the direct extrusion die that is designed using one of the theoretical concepts, Constancy of the Ratio of the Successive Generalized Homogeneous Strain-increment (CRHS), is presented. On the basis of the above concept we used three types of dies that are categorized as uniform (UCRHS),accelerated (ACRHS),and decelerated (DCRH) according to the deformation rates. All dies were with fixed reduction area of 50%. The mixture used (filler with binder) was extruded in round section carbon electrodes carried out at 60oC to 80oC. Ten samples are produced and tested for properties such as electrical resistivity, hardness, density and porosity. The results show that the extrusion die UCRHS is the more efficient die design for the production of carbon electrodes.
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