Hot Pressing Equipment Research Articles

Automated Shape Correction for Wood Composites in Continuous Pressing

The effective and comprehensive utilization of forest resources has become the theme of the global “dual-carbon strategy”. Forestry restructured wood is a kind of wood-based panel made of wood-based fiber composite material by high-temperature and high-pressure restructuring–molding, and has become an important material in the field of construction, furniture manufacturing, as well as derivative processing for its excellent physical and mechanical properties, decorative properties, and processing performance. Taking Medium Density Fiberboard (MDF) as the recombinant material as the research object, an event-triggered synergetic control mechanism based on interventional three-way decision making is proposed for the viscoelastic multi-field coupling-distributed agile control of the “fixed thickness section” in the MDF continuous flat-pressing process, where some typical quality control problems of complex plate shape deviations including thickness, slope, depression, and bump tend to occur. Firstly, the idea of constructing the industrial event information of continuous hot pressing based on information granulation is proposed, and the information granulation model of the viscoelastic plate shape process mechanism is established by combining the multi-field coupling effect. Secondly, an FMEA-based cyber granular method for diagnosing and controlling the plate thickness diagnosis and control failure information expression of continuous flat pressing is proposed for the problems of plate thickness control failure and plate thickness deviation defect elimination that are prone to occur in the continuous flat-pressing process. The precise control of the plate thickness in the production process is realized based on event-triggered control to achieve the intelligent identification and processing of the various types of faults. The application test is conducted in the international mainstream production line of a certain type of continuous hot-pressing equipment for the production of 18 mm plate thickness; the synergistic effect is basically synchronized after 3 s, the control accuracy reaches 30%, and the average value of the internal bond strength is 1.40, which ensures the integrity of the slab. Practical tests show that the method in the actual production is feasible and effective, with detection and control accuracy of up to ±0.05 mm, indicating that in the production of E0- and E1-level products, the rate of superior products can reach more than 95%.

Regenerated cellulose fabric reinforced bio-based polypropylene sandwich composites: fabrication, mechanical performance and analytical modelling

Sandwich composites were fabricated successfully with the balsa wood as core material and regenerated cellulose fabric bio-based polypropylene (PP) composite skins. The regenerated cellulose fabric PP composites were produced using two different methods: the conventional stacking lay-up and directly using PP pellets. Sandwich composites were made using the hot press equipment with the customized mold. The sandwich composite system and bio-composite laminate were designed to achieve very close weight to compare the key mechanical properties that each design can bear. It was evidenced from the experimental results that 416% increase in the bending load bearing property of the part can be obtained when sandwich structure was used. These experimental results were in close agreement with one of the analytical modelling utilised. The drop weight impact test results demonstrated that the sandwich specimen is capable of withstanding more than 6 kN load and absorbing the impact energy of 28.37 J.

Laser transmission welding of dissimilar transparent thermoplastics using different metal particle absorbents

The laser absorbents are necessary in the process of laser transmission welding (LTW) transparent thermoplastics. It has been demonstrated that metal absorbents in LTW have great advantages for achieving a high quality joint, though the decomposition of thermoplastics is difficult to control. Metal particle absorbents with different melting point, including magnesium zinc alloy particles (MZAP), zinc particles (ZnP) and tin particles (SnP), were introduced to investigate the weld morphologies, tensile process and bonding characteristics of the weldments in the present study. The hot-pressing equipment was used to embed the metal particle absorbents in thermoplastic. Lap welding experiments were carried out to investigate the effects of metal particle absorbents and welding parameters (laser power and welding speed) on shear force and the weld morphologies. The discrepancy of shear force–displacement curves, microscopic morphology and element distribution between different weldments were investigated. Compared with the ZnP and SnP absorbents, the weldments with MZAP absorber had the highest shear force of 662 N under the condition of laser power of 35 W and welding speed of 8 mm/s. The underlying reason was attributed to the minimal thermoplastic decomposition and the good interfacial interaction.

Powder Metallurgy Production of Ti-2 Wt Pct Si Alloy: Structural, Mechanical, and Electrochemical Characterization of the Sintered Material

Several commercial alloys use silicon (Si) to improve titanium (Ti) resistance to creep and oxidation at high temperatures and to improve Ti corrosion resistance in acid media. According to the Ti-Si phase diagram, reported stable solid phases in the Ti-rich region are β-Ti, α-Ti, Ti3Si, and Ti5Si3. Nevertheless, very few works in the literature discuss Ti3Si intermetallic production. As such, this work studied the possibility of obtaining an α-Ti-Ti3Si alloy by hot pressing α-Ti supersaturated solid solution powders obtained by mechanical alloying. The consolidation of milled powders was performed using uniaxial hot press equipment. Structural and morphological evolutions during the sintering process were investigated by X-ray diffraction and scanning electron microscopy. Electrochemical behaviors of sintered samples were evaluated by open circuit potential and linear sweep voltammetry. Results show a fine and uniform Ti3Si alloy distribution in the α-Ti matrix produced by the proposed powder metallurgy route. The sintered samples demonstrated high micro-hardness and resistance to sulfuric acid corrosion. Additionally, Ti3Si was shown to have a significant hardening effect on the α-Ti matrix. Electrochemical behavior further demonstrates that a fine and homogeneous Ti3Si distribution in the α-Ti matrix contributes to a more stable superficial oxide layer against sulfuric acid corrosion.

Preparation and properties of hot-deformed magnets processed from nanocrystalline/amorphous Nd–Fe–B powders

The hot-deformed magnets processed from nanocrystalline/amorphous Nd–Fe–B powders were prepared under different hot-pressing temperatures (600–750 °C, at intervals of 25 °C) by the self-made hot-pressing equipment. The microstructure and magnetic properties of hot-deformed magnets prepared at different temperatures were also investigated. When the temperature is above 650 °C, the density of magnet reaches 7.5 g·cm−3. The optimum magnetic properties of magnetic induction intensity of Br = 1.3 T, optimum energy product of (BH)max = 282.5 kJ·m−3, intrinsic coercivity of Hcj = 1130.0 kA·m−1 of hot-deformed magnets are obtained at hot-pressing temperature of 650 °C. X-ray diffractometer pattern shows that the (00L) texture has been obtained. For the microstructural characteristic, on the one hand, the good magnetic performance is attributed to the fine platelet-like grains with an average length of 410–440 nm at the hot-pressing temperature range from 625 to 675 °C. On the other hand, the unaligned coarse grains are observed in all the samples. And the areal fraction of those is gradually increasing with the rise of the hot-pressing temperature, which tends to deteriorate the magnetic properties. The composition map shows the accumulation of Nd/Pr-rich phase in the coarse grains’ region.

Microstructured rubber and its wettability

Microstructured surfaces have been attracting a considerable amount of attention for many practical applications, such as superhydrophobic materials. The key issue in everyday applications of superhydrophobic materials based on microstructured surfaces is their durability because most microstructures are prepared with stiff and fragile materials and are easily broken mechanically. In this study, we focused on vulcanized rubber as a flexible and durable hydrophobic material for the fabrication of microstructured surfaces. Superhydrophobic spiky microstructures were simply prepared from vulcanized rubber by using a silicon micromold and compact hot-press equipment. Owing to the elasticity of the vulcanized rubber, the spike-array arrangements on the rubber surface were reversibly deformed by repeated stretching without destruction of the spiky microstructures. Surface wettability was affected by the spike-array arrangements, which can be controlled by stretching concomitantly with the degree of elongation. This phenomenon was theoretically explained by the wettability transition from a Cassie–Baxter to a Wenzel state considering water penetration into the gaps among the spiky microstructures. The results indicated that microstructured vulcanized rubber surfaces can be applicable to a wide variety of fields because of the superior functions derived from their microstructures. Microstructured surfaces have been attracting a considerable amount of attention for many practical applications, such as superhydrophobic materials. In this report, vulcanized rubber was focused on as a flexible and durable hydrophobic material for the fabrication of microstructured superhydrophobic surfaces. Superhydrophobic spike-array microstructures were simply prepared from a vulcanized rubber by using a silicon micromold, and the arrangements were reversibly deformed by repeated stretching without destruction of the spikes. Surface wettability can be controlled by stretching the vulcanized rubber, and the phenomenon was theoretically explained by the wettability transition from a Cassie–Baxter to a Wenzel state.

Production and characterization of particleboards from cork-rich Quercus cerris bark

Single-layered particleboards were produced from granulated Quercus cerris bark containing cork and phloem granules using standard hot-press equipment and phenol–formaldehyde resin. The experimental boards were tested for thickness swelling, mechanical strength and thermal properties. Scanning electron microscopy observations were carried out to analyze the panel structure. The results showed that Q. cerris bark particleboards had low thickness swelling in water, high resistance to thermal degradation and high calorific values but their mechanical strength was below that of commercial wood particleboards. The produced Q. cerris bark particleboards were adequate for exterior applications where mechanical strength is not the key factor. Potential for process and feedstock optimization was acknowledged.

217 大気中で創製した圧電ファイバ/アルミニウム複合材料の諸特性

This paper describes the characteristics of the metal-core lead zirconate titanate (PZT) fiber/aluminum composite fabricated using the Interphase Forming/Bonding (IF/B) method in the air. In the previous studies, in order to simplify the fabrication procedure and reduce their costs, the metal-core PZT fiber/aluminum composites were fabricated using a compact hot-pressing equipment which enables rapid heating to reduce copper oxidation in the air as a model experiment. In this study, characterization of the composite was investigated by an oscillation test. As the oscillation test, an aluminum plate pasted the composite as an oscillation plate was oscillated by electromagnetic excitation and the output voltage from the composite was measured by an oscilloscope. The results obtained indicate that the output voltage is proportional to the strain, and the output voltage depends on the strain directions. In addition, it was also cleared that phase difference and the displacement of the oscillation plate was changed at a certain strain direction.

J044071 界面層形成・接合法による高機能セラミックス/アルミニウム複合材の大気中創製の試み

This paper describes fabrication of highly functional ceramic fiber/aluminum composites by the Interphase Forming/Bonding (IF/B) Method in the air. In the previous studies, fragile functional fibers such as optical fiber and piezoelectric ceramic fibers have been successfully embedded in an aluminum matrix without losing their functions by the IF/B method using a low-vacuum hot-pressing equipment. In order to simplify the fabrication procedure and reduce their costs, optical fiber/aluminum composites are fabricated using a compact hot-pressing equipment which enables rapid heating to reduce oxidation in the air. In this study, the effects of hot-pressing conditions such as pre-pressure, heating rate and holding time in the air on the microstructure of the composites and the bonding strjpnth of the matrix aluminum plates are examined, and appropriate conditions are successfully obtained.

J044102 界面層形成・接合法による脆性機能繊維/アルミニウム複合材料の大気中創製の試み([J04410]知的材料・構造システム(10))

This paper proposes a method for simple and easy fabrication of brittle and highly functional ceramic fiber/aluminum composites by the interphase forming/bonding (IF/B) method in air. In the previous researches, brittle functional fibers such as optical fiber and piezoelectric ceramic fiber have been successfully embedded in an aluminum matrix by the IF/B method using copper insert in a vacuum. In this study, optical fiber/aluminum composites were fabricated by using the newly developed compact hot-pressing equipment capable of quick operation in air, and the main results can be summarized as follows: 1) By changing the fabrication atmosphere from vacuum to air, the oxidation could be improved simply by increasing the heating rate, which became possible by using the new compact equipment. 2) The pre-pressing process in the IF/B method in air was proved to be useful to minimize the oxidation

Porous CuAlMn Shape-Memory Alloys with Controlling Porosity and Pores’ Structural Parameter Produced by Sintering-Evaporation Process

The porous Cu-11.9Al-2.5Mn (wt %) shape memory alloys with open-cell structure were successfully prepared by Sintering-evaporation Process method. A mixture powders with CuAlMn and NaCl powder were hot pressed at 780°C for 3hrs in the hot-pressing equipment with dynamic vacuum of 0.001Pa, and then pressure force was unloaded and the sintering temperature was heated up to 990°C, the NaCl was melted and evaporated completely at 990°C for 24hrs. The shape and size of the pores among the porous CuAlMn shape memory alloys are almost the same as those of NaCl powders, the pores are interconnected. The microstructure, mechanical property and phase transformation behavior of the sample have been studied. The results show that the porous CuAlMn SMAs with controlling porosity and pores’ structural parameters can be prepared by Sintering-evaporation Process, and their phase transformation behaviors are similar to that of conventional bulk Cu-11.9Al-2.5Mn (wt %) shape memory alloys.

Ｎｉ基金属ガラス粉末の温間塑性加工・焼結特性

The formability and sintering behavior of Ni60Nb15Ti20Zr5 metallic glass powder prepared by gas atomizing was investigated using precise hot press equipment. The structure of atomized metallic glass powder depended on its particle size, and only glassy phase was observed when the particle size was under 53μm. The glass transition temperature (Tg), crystallization temperature (Tx), and supercooled liquid region (ΔTx=Tx-Tg) of the Ni-based metallic glass powder was 838 K, 888 K and 50 K, respectively.The hot press sintering under the precise control of temperature and pressure was conducted. The densification behavior depended on only working temperature, and the Ni-based metallic glass powders were consolidated to nearly full density by hot press sintering with working temperature range 863-883 K. On the other hand, the crystallization behavior depended on working time as well as working temperature. In the experimental study this time, the hot press condition achieving both full densification and no crystallization was temperature of 868 K and pressure of 200 MPa. The sintered body of full densification and no crystallization exhibited high corrosion resistance nearly equal to Alloy C-276.

Development of Thermoelectric Cooling Devices with Graded Structure

Every thermoelectric material shows high performance at a specific narrow temperature range. The temperature range with high performance can be expanded by joining the materials with different peak temperature. This is the concept of a functionally graded material (FGM) for thermoelectric materials. Bismuth telluride is the best material for cooling devices at around room temperature. Then we investigated the thermoelectric cooling properties for bismuth telluride with two step graded structure. FGM samples were fabricated by three methods. The first FGM was synthesized by in situ method. The second one was fabricated by joining in a hot-press equipment. The last one was composed by joining with solder. Thermoelectric cooling properties were evaluated by observing the maximum temperature drop to electric current when the high temperature side was kept constant. The large temperature difference was obtained when the proper configuration of thermoelectric materials along the temperature gradient were performed. The coincidence of optimum electrical currents of composing materials is also essential to obtain the high cooling performance.

遠心焼結によるＣｕ厚膜のち密化とクラック除去

Films with thickness ranging from several ten μm to several mm are of great interest due to their application or necessity in highly integrated, small electric devices. In this work, we report the processing merit of a novel centrifugal sintering, which densifies metallic film by applying high pressure, in the absence of a pressure medium such as graphite bar in hot-pressing equipment. Cu thick film on SiO2 substrate has been prepared for studying the sintering behaviour. It is observed that the pores and cracks in the specimens were drastically removed, and then promoted its densification by centrifugal firing, compared with conventional firing.

HOT PRESSING OF METALLIe CARBIDES

AbstractA survey is presented of published work on the hot pressing of metallic carbides. On the basis of a comparison of the apparatus described in the literature, hot-pressing equipment has been built, designed for vacuum sintering using resistance heating, a combination that has many advantages.Nine metallic carbides from Groups IV, V, and VI of the Periodic Table were hot pressed to high densities, as well as mixed carbides and carbides of varying carbon content. Compacting details are summarized, together with data covering lattice parameters and microhardness.The purity of the metallic carbides has great significance as regards the sintering mechanism. This is demonstrated both by theory and experiment.