Hot Die Steel Research Articles

Optimizations of friction stir welding process parameters of AA6063 Aluminium alloy by Taguchi technique

The effects of axial force, rotational speed, welding speed, and shoulder penetration on various Process parameters of Aluminium alloy 6063 butt joint produced by Friction Stir Welding have been analyzed. The mechanical properties like tensile strength, Yield strength, and % Elongation have been tested using a 6 mm thickness plate. The tool used for experimenting was Hot Die Steel (HDS). The welding quality can be improved by enhancing the mechanical properties and minimizing the defects. Hence, analyzing & examining the mechanical or physical properties and other relevant significant factors would enhance the weldability. Tensile Strength (T.S.), Percentage of Elongation & Yield Strength (Y.S.) of FSW Al 6063 alloy has been carried out under different processing conditions using Taguchi's experimental design.

Strength Behaviour of Hot Die Steel with Respect to its Heat Treatment

The surface temperature of hot die steel reaches typically up to 550ºC or above during processes like hot extrusion and casting non-ferrous material. The present paper explores the impact of austenitizing temperature as well as tempering temperature on the tensile strength of hot die steel. Heat treatment is done at three different austenitizing temperatures of 1010ºC, 1030ºC, and 1050ºC, followed by tempering done at two different temperatures of 540ºC and 580°C. Tempering is done twice for two hours. Metallographic grinding, polishing, and then etching using 2% Nital is done to investigate the microstructure of hot die steel with respect to its heat treatment. It is found that the grain size of hot die steel increases with an increase in austenitizing temperature. The impact on tensile strength of hot die steel for its heat treatment is examined by conducting the uniaxial tensile test to fracture. And investigation of the morphology of the fracture surface produced after the tensile test is done. It was found that hot die steel with large grain size exhibits lesser tensile strength. Whereas, the one having smaller grain has higher tensile strength that is found to be in accordance with the Hall-Patch equation.

Effect of Process Parameters during Friction Stir Welding of Al 6063 Alloy

In the Present paper, the effects of axial force, rotational speed of the FSW tool, welding speed and shoulder penetration on various mechanical properties of Aluminium alloy 6063 butt joint produced by Friction Stir Welding have been analyzed. The mechanical properties like tensile strength, Yield strength and % Elongation have been tested using 6 mm thickness plate. The tool used for conducting the experiment was Hot Die Steel (HDS). The welding quality can be improved by enhancing the mechanical properties and minimizing the defects. Hence, analysing & examining the mechanical or physical properties and other relevant significant factors would help to enhance the weld reliability. Tensile Strength (TS), Percentage of Elongation & Yield Strength (YS) of FSW Al 6063 alloy has been carried out under different processing condition using Taguchi’s experimental design. An optimum result has been obtained using main effects plot using S/N ratio values. The rotation speed of the FSW tool has been found dominant factor for TS followed by feed and shoulder penetration. Shoulder diameter shows the least effect on TS compared to parameters like Percentage of Elongation & Yield Strength (YS).

FE SIMULATION AND EXPERIMENTAL VALIDATION OF POWDER MIXED EDM PROCESS FOR ESTIMATING THE TEMPERATURE DISTRIBUTION AND VOLUME REMOVED IN SINGLE CRATER

This study reports the results of a finite element simulation of powder mixed electric discharge machining process for H11 Hot Die steel material using relevant boundary conditions and reasonable assumptions. The crater shape was developed using simulated temperature profiles to estimate the volume removed in a single crater. The temperature distribution on the workpiece was used to predict the cooling rate and calculate the stresses generated due to thermal loading. Subsequently, the simulation results were experimentally validated by physically measuring the crater shape and volume. From the results it was concluded that about 25% of heat is transmitted to the workpiece during machining at the process conditions used in the experiment. The microscopic pictures showed bigger craters with increase in current. The machined surface showed overlapping craters with surface cracks suggesting a high cooling rate.

Optimization of powder mixed electric discharge machining using dummy treated experimental design with analytic hierarchy process

The analytic hierarchy process (AHP) is widely used for the optimization of multiple responses from an experimental study. In the present study, a method to obtain more reliable global weight of different alternatives has been described for a powder-mixed electric discharge machining (EDM) process. Seven different process parameters were tested to study their effect on material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) using a specially designed Taguchi orthogonal array that could accommodate factors with varying number of levels. A three-level array L27 was modified to include two-level factors using dummy treatment. The process conditions that affected the three responses were identified and optimized together using AHP for high carbon high chromium (HCHCr), EN31 and hot die steel (HDS) workpiece material. Addition of powder in the dielectric improved the MRR as the electrical conductivity of powder reduces the dielectric insulating strength. Current, powder, and electrode material significantly affected the TWR. Kerosene as dielectric was observed to be a superior alternative than EDM oil. Graphite electrode worked best for HCHCr and EN31 and W–Cu electrode worked best for HDS as they globally optimize the three output variables. Also, Cu powder suspended in the dielectric resulted in an optimal solution for HCHCr and HDS and tungsten powder was seen to be a better choice for EN31 to globally optimize the responses. To overcome problems of poor finish at high current setting in EDM, the dielectric should be mixed with powder.

Surface Modification of High Carbon High Chromium, EN31 and Hot Die Steel Using Powder Mixed EDM Process

This paper investigates the effect of electric discharge machining (EDM) process parameters and powder mixed in dielectric on surface properties of three die steel work materials; namely High Carbon High Chromium (HCHCr), EN 31 and Hot Die Steel (HDS). The mechanism of material deposition from the suspended powder and/or tool electrode is reported. Current emerged as the most significant factor affecting the microhardness along with powder mixed in the dielectric and electrode material. Amongst the two electrode materials, copper-tungsten along with tungsten powder had the best microhardness. Selected samples were analyzed for X-ray Diffraction (XRD) followed by microstructure analysis using a Scanning Electron Microscope (SEM). The results showed significant material transfer from the electrode as well as powder either in free form or in compound form. It was concluded that surface modification of die steels can be done by incorporating simple modifications in the EDM set-up resulting in higher microhardness and superior wear resistance of the machined surface.

PARAMETRIC INFLUENCE AND OPTIMIZATION OF WIRE EDM OF HOT DIE STEEL

Wire-cut Electro Discharge Machining (WEDM) is a special form of conventional EDM process in which the electrode is a continuously moving conductive wire. The present study aims at determining parametric influence and optimum process parameters of Wire-EDM using Taguchi's technique and a Genetic algorithm. The variation of the performance parameters with machining parameters was mathematically modeled by Regression analysis method. The objective functions are defined as Dimensional Error (DE), Surface Roughness (SR) and Volumetric Material Removal Rate (VMRR). Experiments were designed as per Taguchi's L16 Orthogonal Array (OA) wherein Pulse-on duration, Current, Pulse-off duration, Bed-speed and Flushing rate have been considered as the important input parameters. The matrix experiments were conducted for the material Hot Die Steel (HDS) having the thickness of 40 mm. The Heat Affected Zone (HAZ) characteristics of the eroded materials were assessed by Scanning Electron Microscope (SEM) and the microhardness of the material was tested using Vickers microhardness tester. The results of the study reveal that among the machining parameters, it is preferable to go for smaller pulse-off duration for achieving overall good performance. Regarding pulse-on duration, higher values are recommended for error constrained machining with higher MRR and constrained/limited values for attaining good surface texture. Smaller current is suggested for better surface finish/texture control, medium range for error control and high value for MRR. Finally, the validation exercise was performed with the optimum levels of the process parameters. The results confirm the efficiency of the approach employed for optimization of process parameters in this study.

Transformation Plasticity of Hot-Die Steel During Hardening

The paper presents the results of investigations of transformation plasticity of hot-die steel (high temperature–resistant steel used in high-temperature deforming) during hardening. A special device was used to evaluate transformation plasticity and determine the maximum normal bending stress, modulus of transformation plasticity for medium alloyed and medium carbon steel.

Oxidation Resistance of a Hot-Die Steel (H13) with Al Coating and High Current Pulse Electron Beam Treatment

A two-step surface treatment process has been developed, which combines arc deposition with High-Current Pulsed Electron Beam (HCPEB) post treatment. Arc deposition produced an Al-coating ∼10 μm thick on H13. The coating was subsequently bombarded with HCPEB. Due to the rapid surface heating, melting and cooling, a part of the Al-coating was melted into the substrate surface, forming a mixed surface alloying and intermetallic layer. Experimental results revealed that the high temperature oxidation rate was reduced by a factor of 40 compared to the untreated steel. The mechanisms of the improvement in oxidation resistance were discussed according to the experimental results.

Effects of cryo-cooling in grinding steels

The grinding process is inherently characterised by high specific energy and high temperature, which are responsible for high wheel loading, increased grinding forces, reduced metal-removal rate, rapid wheel wear and deterioration in the quality of the ground surface through oxidation, the induction of tensile residual stress and micro-cracks. These problems become more acute when the product is of HSHR material and subjected to dynamic loading while functioning. Therefore, in industry the user should pay special attention to control and optimise all the significant parameters for minimising the afore-said problems, aiming at higher grindability, productivity and overall economy in grinding. The basic principles of controlling such high temperature are: (i) proper selection and optimisation of wheel and process parameters; (ii) the removal of heat from the grinding zone by the application of proper grinding fluid. Profuse cooling with conventional grinding fluids, even in the form of mist or jet, is virtually unable to solve the problem. However, cryogenic cooling by agents such as liquid nitrogen is expected to meet this challenge. In the present work, specimens of different steels, namely MS, HCS, cold- and hot-die steel and HSS, have been surface ground at different infeeds under dry conditions and with soluble oil and liquid nitrogen. The effects of such cryo-cooling relative to soluble oil and dry grinding have been investigated in respect of chip formation, grinding forces, specific energy, burning and surface characterisation. The experimental results indicate that the grinding temperature and burning decreased remarkably under cryo-cooling. Thermal damage of the ground surface has been reduced substantially by cryo-cooling, but to different degree in different steels. Cryo-cooling also enables retention of the wheel sharpness for a longer period and results in less force and specific energy being required.

Depositions of Welded Coatings to Improve Hot Wear and Thermal Fatigue Resistance of Hot Die Steel

Depositions of Welded Coatings to Improve Hot Wear and Thermal Fatigue Resistance of Hot Die Steel

AL TECH POTOMAC A

Abstract AL TECH POTOMAC A has well-balanced strength and toughness which make it especially suitable for a wide variety of hot-die steel applications, including those involving severe coolants. Its outstanding mechanical properties make it useful for many non-tooling requirements such as aerospace components. For more specialized needs, the manufacturer offers special melting processes that enhance this steel's fatigue properties and transverse tensile ductility. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on high temperature performance as well as forming, heat treating, and machining. Filing Code: TS-478. Producer or source: AL Tech Specialty Steel Corporation.