Steel Mold Research Articles

Preparation and characterization of vitrified tiles from kaolinite clay – waste container glass mixture by sintering method

In this study, vitrified ceramic tiles were made by sintering a mixture of recycled waste container glass powder (RWGP) and kaolinite clays sourced from Nigeria. Initially, waste container glass (transparent color) was obtained from a municipal waste deposit, washed, and crushed before fine milling and sieving to obtain RWGP of approximately 75 µm. Prior to use, the as-received kaolinite clays were also beneficiated and sieved. Three body mixes (VT1, VT2, and VT3) containing 80 – 90 wt. percent RWGP with kaolinite clays and feldspar were homogeneously blended and compacted in a steel mould measuring 200 x 180 x 10 mm. The green compacts were allowed to dry at room temperature before sintering at 1200oC for 2 hours. To evaluate the properties of the developed vitrified tiles, physical, mechanical, phase, and microstructure investigations were carried out. The results showed that bulk density increases across the series, while porosity was 0.5 percent for all tested samples, which is in accordance with ISO 13006. VT2 had higher hardness (6.71 MPa) and compressive strength (2.44 MPa). Quartz and wollastonite were the major phases identified by XRD, with albite, orthoclase, and calcite also present. The microstructure revealed a densified morphology typical of a clay–quartz structure, with little glassy phase resulting from the limited reaction of glass with the clay during sintering.

Improvement of surface characteristics of mold steel using laser cladding and shock peening

In the automobile industry, improving the properties of the mold improves productivity and reduces the defect rate of the product. In this study, a laser heat source was used to improve the properties of the mold. To improve the surface strength of the mold steel, laser cladding was applied to form a surface alloy layer. In addition, an experiment was performed to improve the tensile residual stress of the cladding layer by applying laser shock peening. A continuous wave high-power fiber laser was used for laser cladding, and a high-peak Nd:YAG pulsed laser system was used for laser peening. As a result, an alloy layer harder by more than 1.5 times than the base material was formed on the surface of the mold steel through laser cladding, and the tensile residual stress of the laser cladding layer with peening applied was improved by about 50%.

Multi-scale analysis of void evolution in large-section plastic mold steel during multi-directional forging

Multi-scale analysis of void evolution in large-section plastic mold steel during multi-directional forging

Simulation Study on Surface Topography and Roughness in Milling Process of Curved Die

Surface texture features such as surface morphology and surface roughness control the corrosion resistance and fatigue resistance of parts. Due to the complex structure of tool and workpiece in milling process, the traditional experimental method is not suitable. Based on the cutting edge line model, the tool trajectory model and the point cloud model of the convex surface workpiece, the simulation model of the surface topography and surface roughness of the convex surface hardened steel mold milling process was established, and the simulation of the surface topography and roughness was realized by combining with the Z-map simulation algorithm. The correctness of the model is proved by the confirmatory experiment. Based on Taguchi method and gray relation analysis method, the sensitivity of surface roughness to machining inclination and cutting parameters is analyzed. It is concluded that the spindle speed has the greatest influence on the roughness and the roll angle has the least influence. The research results provide a theoretical basis for the optimization of cutting parameters in the machining process.

Microstructure of Ultrafine Acicular Bainite and Mechanical Properties of 3Cr2MnNiMo Mold Steel during Austempering

Herein, the effect of austempering treatment on martensite/bainite multiphase microstructure evolution and mechanical properties of 3Cr2MnNiMo mold steel are investigated, and the mechanical properties are compared with the conventional quenching and tempering (QT) treatment. It indicated that the morphology of martensite/bainite can be effectively tailored by changing the austempering temperature. With the increase of temperature from 280 to 360 °C, the microstructure changes from tempered martensite + bainite + blocky retained austenite (RA) to martensite + coarse bainite plate + blocky RA and irregular martensite/austenite (M/A) island. When the temperature reaches 420 °C, the martensite content reaches the maximum. The bainite morphology is surprisingly transformed from coarse bainite plate to ultrafine acicular shape owing to the reduction of the bainitic driving force and the sharp increase of carbon diffusion coefficient. Moreover, blocky RA and M/A islands disappear and are replaced by nanoscale filmy RA. The alternating distribution of variants has a refinement effect on the microstructure and the effective grain size reaches a minimum value. Compared with the conventional QT treatment, the tensile strength of austempering at 420 °C increased by 702 MPa, but the toughness and ductility levels are almost the same.

Research on Modeling of Milling Force of Ball-End Mill Cutter in Multi-hardness Splicing Area of Automobile Panel Die Steel

The structure and the cavity surface hardened steel mold of automobile cover is very complex. In the stamping process, the local structure bears higher extrusion stress than the type surface, which often causes local wear and even cracking. The process of multi hardness splicing joint is applied to ensure the service life of the die according to the features of each part of the mold. The impact load caused by the repeatedly cut-in which always leads to the instability of cutting force in the whole process. The machining quality of the mold surface is reduced. Aiming at the machining process of the ball-end milling cutter in the mold splicing area, the impact at the moment of contact between the cutter and the workpiece is analyzed. The instantaneous chip thickness model that considers impact factors and the state model that calibrates the cutting state by coefficients is established. Finally, the prediction model of the milling force of the splicing area is obtained. The model is verified based on the machining cutting force measurement experiment in the case of die hardened steel Cr12MoV with single hardness and multi-hardness splicing. The average prediction error of experiments and simulation results is within 10%, which proves the accuracy of the model. The results show that the model has certain guiding significance for the actual processing of the splicing area of automobile mold cover parts.

A comparative study of retention of cement retained implant prosthesis cemented with different luting cements

Purpose: The study was conducted to evaluate the retentiveness of specifically formulated implant cements and compare its retentiveness with a commonly used noneugenol zinc oxide luting cement and also to assess the influence of abutment height on the retentiveness of these cements. Materials and Methods: A master stainless steel mold was used to mount snappy abutment-implant analog complex in acrylic resin. A total of six stock abutments (Osstem TS®) of 4 mm and 5.5 mm height with their analogs were used. A total of 66 ceramill® Sintron metal copings fabricated using computer-aided design/computer-aided manufacturing system and divided into six groups (n = 11) according to the height (three 4 mm abutment and three 5.5 mm abutment). The cements that were compared were a Noneugenol zinc oxide provisional cement , Dual Cure Resin Cement and a Zinc Phosphate Cement . After cementation samples were immersed in artificial saliva for 7 days and subjected to a pull-out test using a universal testing machine at a crosshead speed of 1 mm/min. The load required to de-cement each coping was recorded and analyzed using one-way ANOVA, post hoc multiple comparison, and independent t-test.

Effect of Slag Pool Rotation on the Structure of a High-Speed Steel in a Current-Supplying Mold

Effect of Slag Pool Rotation on the Structure of a High-Speed Steel in a Current-Supplying Mold

The study of chip characteristics and tool wear in milling of SKD61 mold steel

The study of chip characteristics and tool wear in milling of SKD61 mold steel

Experimental and Analytical Modeling of Flexural Impact Strength of Preplaced Aggregate Fibrous Concrete Beams.

Preplaced aggregate fibrous concrete (PAFC) is a revolutionary kind of concrete composite that is gaining popularity and attracting the interest of academics from across the world. PAFC is a uniquely designed concrete prepared by stacking and packing premixed fibers and coarse aggregate in a steel mold. The gaps between the fibers and aggregates are subsequently filled by injecting a cement grout with high flowability. This study investigates the impact performance of three different sizes of PAFC beams. Steel and polypropylene fibers were used in a 3% dosage to make three different beam sizes, measuring 550 × 150 × 150 mm, 400 × 100 × 100 mm, and 250 × 50 × 50 mm. According to ACI Committee 544, all beams were subjected to a drop weight flexural impact test. Compressive strength, impact energies at initial crack and failure, ductility index, and failure mode were evaluated. Additionally, analytical modeling was used to compute the failure impact energy for the fibrous beams. The results showed that the addition of fibers increased the capacity of the tested beams to absorb greater flexural impact energy. Compared to polypropylene fibers, steel fibers had better crack propagation and opening resistance because of their higher tensile strength and crimped and hooked end configuration. For all large-size beams, the analysis of the percentage increase in impact energy at the failure stages was found to be 5.3 to 14.6 times higher than the impact energy at cracking.

Injection molding and characterization of microtextures on polycarbonate using laser textured inserts

ABSTRACT The purpose of this paper is to demonstrate the easy manufacturing and quick characterization of several microtextured functional surfaces on two transparent thermoplastics of general interest for several industrial sectors. Microtextured polymeric surfaces with special optical, tribological and easy-cleaning properties were manufactured via isothermal injection-molding using laser-microtextured steel mold inserts. For that purpose, conventional injection molding of two chosen amorphous transparent polymers (polycarbonate, PC, and polymethyl methacrylate, PMMA) utilizing laser-microtextured steel inserts was carried out, and a detailed morphological and functional characterization of the injected specimens was conducted later on. We also report on the suitable process conditions for the injection molding of these specimens using design of experiment (DOE) techniques. The analysis of the degree of replication (DR%) on the injected samples shows that mold temperature and injection speed are the most relevant parameters to obtain a successful replication and confirm the viability of conventional injection molding as a processing technique to obtain microtextured functional surfaces in amorphous transparent thermoplastics. The success of the procedure is further checked by the confirmation of the obtained surface functionalities by various standard and self-developed methods.

Dynamic wetting characteristics of submicron‐structured injection molded parts

AbstractThe generation of submicron structures on plastic part surfaces can be used to modify their wetting properties allowing the creation of superhydrophobic surfaces. The modified wetting behavior can allow functionalities such as fluid collection or transport, which are critical for microfluidics. Consistent manufacturing is achieved through surface replication and process characterization. In this work, submicron structures were generated on steel mold inserts using ultrafast femtosecond laser and then replicated by micro injection molding on polypropylene and polylactic acid. Samples with Laser‐Induced Periodic Surface Structures (LIPSS) were fabricated using a femtosecond laser and characterized to investigate the effects of mold temperature, texture orientation, and material selection on the dynamic contact angle. The dynamic wetting functionality of the surfaces was investigated by analysis of the advancing and receding contact angles. The hysteresis obtained from the dynamic measurements provides information about the fluid/texture interaction dynamics. The experimental results show that the effects of mold temperature and drop orientation are only significant for the advancing contact angles. The large contact angle hysteresis suggests a parahydrophobic wetting behavior for the manufactured plastic parts.

RESEARCH OF FEATURES OF CONSOLIDATION OF ANTI-FRICTION MATERIALS BASED ON POWDER MIXTURE Cu–Pb–C

The article represents the results of research of various methods of obtainingantifriction material "copper-lead-graphite" by methods of powder metallurgy. With the help of hotvacuum electroconsolidation of powders, which is effective for refractory materials, the conditionsfor separate cold pressing are determined, namely, product formation at 500 MPa and sintering at900 °C, which is more productive for metal powders.The initial formation of the samples was carried out in a collapsible steel mold on a hydraulicpress with a force of up to 200 tons from a mixture of powders of copper, lead and graphite, whichhad dimensions of 60–200 μm. Sintering was performed in a vacuum oven at temperatures of 700–900 °C for 20–30 minutes. To obtain a density of more than 5.6 g / cm3, it is necessary to significantlyincrease the pressure during the formation of powders. During the formation of the dry mixture,compression transverse cracks appear.Liquefied kerosene was selected from the list of studied organic liquids, which allowed to obtainhigh-quality products without cracks with a density of 5.6–5.9 g/cm3 at a load force of about 500 MPa. Sintering was performed in an inert nitrogen environment, which reduced lead losses to2–5 % at temperatures above 700 °С. Nitrogen was first supplied to the vacuum chamber to apressure of 1 atmosphere, and after increasing the temperature in the chamber, the nitrogen pressurerose to 1.2 atm.The hardness of the obtained samples was 42–46 HB according to Brinell (135–150 MPa).Machining of samples with different cutting tools was performed at different speeds and showed goodmachinability. Processed parts during storage have not changed their size. With the help of thedeveloped technology it is possible to produce composite materials with a density of 4.4–6.2 g/cm3and a Brinell hardness of 30–48 HB (99.9–159 MPa).

High-temperature tribological behaviours of H13 hot work mould steel by low-temperature plasma nitriding process

ABSTRACT H13 hot work mould steel was treated via low-temperature plasma nitriding (LTPN) to obtain a nitrided layer. The morphologies, phases and hardness of the nitrided layer were characterised using a scanning electron microscope (SEM), X-ray diffraction (XRD) and Vickers hardness tester, respectively. The friction-wear behaviours of the nitrided layer at 500°C were investigated using a wear tester, and the effects of normal loads on the coefficient of friction (COF) and wear rate were discussed. The results show that the nitrided layer was composed of γ’-Fe4N and ϵ-Fe2–3N hard phases. The average COFs of the nitrided layer under the normal loads of 2, 4 and 6 N were 0.85, 0.57 and 0.50, respectively; and the corresponding wear rates were 7.30 × 10−5, 6.96 × 10−5 and 1.40 × 10−4 mm3 N−1 m−1, respectively, indicating that the wear resistance under the normal load of 4 N is the best among the three kinds of normal loads. The nitrided layer effectively improves the anti-wear performance of substrate, and the oxidisation wear decreases with the increase of normal load.

Design and strength optimization method for the production of structural lightweight concrete: An experimental investigation for the complete replacement of conventional coarse aggregates by waste rubber particles

End-of-life tires are a challenging waste because of their non-biodegradable properties, high production volume, and low utilization rate. Extensive research is currently being undertaken to look for various applications of waste tire rubber in the concrete industry to improve their utilization rate and significantly increase the uptake of this waste material. However, low strength and poor bond performance between rubber aggregates and cement matrix are hindering its application in the concrete industry. This paper introduces an innovative method of prestressing the coarser rubber aggregates (RAs) to address these challenges and limitations found in the critical literature review. Two steel mould rigs were newly designed for manufacturing the rubberized concrete (RuC). Three different mix designs containing 100% replacement of conventional coarse aggregates were prepared using (i) two different sizes of rubber particles and (ii) the addition of steel fibers. Density, SEM-EDS analysis, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity were undertaken to evaluate mechanical performances. The experimental results depict that this novel preloading method can bring a maximum of 97%, 59%, and 20% increase in compressive strength, flexural and tensile strength compared to that of the normal RuC, respectively. In addition, it provides a significant improvement in the interfacial transition zone between the matrix and RAs. This study demonstrates the efficient scientific recycling procedures in manufacturing the RuC with a maximum compressive strength of 18 MPa (density of 2000 kg/m3), which can be considered structural lightweight concrete as per ACI 213R-14 and Eurocode 2 recommendations.

Flexural strength and compressive strength of conventional glass ionomer luting cement and resin modified glass ionomer luting cement after incorporation of chlorhexidine

Introduction Glass ionomer luting cements (GIC) and Resin modified glass ionomer luting cements (RMGIC) are used to attach and seal fixed dental prostheses to teeth. Despite of their anticariogenic properties, there is still existence of caries. Studies have shown incorporation of chlorhexidine (CHX) can increase its antimicrobial action without affecting their physical properties. Objectives of the study The objective was to evaluate the effect of incorporation of CHX on flexural and compressive strength of conventional GIC and RMGIC. To compare the strength of both the cements on incorporation of CHX. Methodology: Forty bar shaped specimens and cylindrical specimens of both the cements were prepared for flexural strength and compressive strength testing using stainless steel mold. CHX powder was incorporated into experimental groups of both luting cements in a concentration of 1%. Specimens were stored in artificial saliva for 24 hours. Flexural strength and compressive strength of the specimens was determined using universal testing machine. Morphological evaluations for fractured surfaces were done using scanning electron microscopy. The data was statistically analyzed using independent sample t-test. Result: The results of the study showed that, addition of 1% CHX decreased compressive and flexural strength of both conventional GIC and RMGIC. On addition of CHX RMGIC showed better compressive and flexural strength compared to conventional GIC. Conclusions: The Chlorhexidine (CHX) amount should be kept below 1% for both the cements to sustain their strength.

Analysis of the Warpage Phenomenon of Micro-Sized Parts with Precision Injection Molding by Experiment, Numerical Simulation, and Grey Theory.

In this study, we determined the effects of design and processing parameters of precision injection molding (PIM) to minimize warpage phenomena of micro-sized parts using various plastics (polyoxymethylene (POM), acrylonitrile-butadiene-styrene (ABS), polypropylene (PP), polyamide (PA), and ABS+ polycarbonate (PC)). We applied a numerical simulation (Moldflow) to determine the runner’s balance in multi-cavities of the micro-sized part and simulate the warpage phenomenon of micro-parts with PIM. We used simulation data to fabricate a steel mold by computer numerical control (CNC) machining. In this, we study manufactured a micro-sized part and measured its warpage value using various PIM process parameters (melt temperature, mold temperature, injection pressure, and filling time). In order to obtain optimal results (i.e., minimum warpage), we employed the Taguchi method and grey theory to discern the influence of each process parameter on PIM. Finally, we determined that the most significant PIM process parameter influencing the warpage phenomenon of micro-sized parts was the mold temperature, regardless of whether in terms of the experimental results, numerical simulations, or grey theory. The PA material had the most suitable properties for application for micro-sized parts, regardless of whether in terms of experimental results, numerical simulations, or grey theory for PIM. This study also illustrates that micro-sized parts can be fabricated by PIM without the use of micro-injection molding, and we determined that the mold temperature required for molding does not need to be higher than the glass-transition temperature of the material.

Process Optimization of Robotic Polishing for Mold Steel Based on Response Surface Method

Aimed to reduce surface roughness (Ra) and improve surface quality of mold steel, the optimizations of process parameters for robotic polishing, such as polishing pressure, feed speed and rotating speed of tool, are accomplish in this research. The optimum range of each parameter is obtained according to a single factor experiment, and the central composite design experiments on the three polishing parameters are conducted to establish a prediction model of surface roughness. Furthermore, a significance test of the prediction model is carried out through variance analysis. The optimum polishing parameters are obtained based on the analysis of response surface, and are then adopted in the polishing experiments of mold steel for validation. The experiment result of model verification indicates that the relative errors of predicted Ra ratio and actual Ra ratio are within the allowable range (maximum is 13.47%). It proves the accuracy of the roughness prediction model. Meanwhile, the experimental results of multipath polishing show that the surface roughness decreased effectively after polishing with the optimum polishing parameters. The prediction model of surface roughness and optimum polishing parameters are helpful to improve surface quality in robotic polishing for mold steel.

Optimal Processing Parameters of Transmission Parts of a Flapping-Wing Micro-Aerial Vehicle Using Precision Injection Molding.

In this study, we designed and fabricated transmission parts for a flapping-wing micro-aerial vehicle (FW-MAV), which was fabricated by precision injection molding, and analyzed its warpage phenomena. First, a numerical simulation (Moldflow) was used to analyze the runner balance and temperature, pressure, and stress distributions of the base, gears, and linkage of the transmission structures in an FW-MAV. These data were then applied to fabricate a steel mold for an FW-MAV. Various process parameters (i.e., injection temperature, mold temperature, injection pressure, and packing time) for manufacturing transmission parts for the FW-MAV by precision injection molding were compared. The Taguchi method was employed to determine causes of warpage in the transmission parts. The experimental results revealed that the causes of warpage in the transmission parts were, in order of importance, the mold temperature, injection pressure, packing time, and injection temperature. After the transmission parts were assembled on the FW-MAV, experiments revealed that the MAV could achieve a flight time of 180 s. Mass production of the FW-MAV by precision injection molding could potentially produce substantial savings in time, manpower, and cost.

Research on eddy current testing method of mould molten steel

Abstract A double eddy current sensor is proposed to measure the liquid level of molten steel in mold and the liquid level of protective slag molten pool. The finite element models of the sensor and the measured object are established by using the finite element COMSOL simulation software. According to the different conductivity of each material in the mold, the measured object is set with the composition layer structure, and the liquid level of molten steel and the liquid level of protective slag molten pool are obtained by using double eddy current sensor and double frequency measurement. The factors affecting the measured value are analyzed and the structure of the sensor is optimized to detect the liquid steel in a large distance within 50-160mm, and the liquid level of molten pool in the mold is measured by high-frequency coil.