Mold Size Research Articles

Industrial Research on Broadening of Slab in Continuous Casting Process

In order to check the general existence of broadening of slab and the reasons of formation, the broadening of slab was investigated on the basis of several industrial manufactures of continuous casting. The results show that slab broadening commonly exists in the process of continuous casting. The causes of broadening were ruled out of the consideration of the change of mold size or the change of technical parameters. The results reveal that the broadening of slab probably results from the static pressure of molten steel and the force from driving rolls. At the same time, online observations of three grades of steel in the process of continuous casting reveal that the ratio of ultimate broadening of slab ranges from 1.27% to 3.00%, and even arrives at 4.4%.

Experimental Study on Silicone Rubber Mold Design for Thermal Expansion RTM

The silicone rubber mold in thermal expansion resin transfer molding was used to generate high thermal expansion pressure on the preform, having an advantage over fabrication of complex-shaped composites. The mold thickness-fiber content equation was derived to design the mold size. It was established based on two parts in this article, the pressure and corresponding fiber content data obtained from compaction experiment and the mold thickness-pressure equation gained from the calculation theory for mold design. Considering the influence of process parameters on the mold size, the synergistic effect of temperature, mold thickness, and the fiber content has been analyzed. The results indicate that mold thickness is inversely proportional to the temperature when the desired fiber content remains constant. When the final fiber content of the part is set, every unit decrease in temperature leads to increasing amplitude of mold thickness. When the temperature variation is unchanged, with every unit increase in fiber content the amplitude of mold thickness grows larger. Moreover, according to the temperature inequality, the temperature variation should be above the critical value so as to make the mold designable.

EFFECT OF GRAIN SIZE OF THE RECLAIMED MATRIX CERAMIC MOULDS USED IN THE LOST WAX TECHNOLOGY ON THE STRENGTH AT HIGH TEMPERATURE

Production technology of investment casting involves transmitting the elements of shape, dimensions and properties by filling in the appropriate liquid metal ceramic forms reproduccd by a model made of wax removed by melting it. The manufacturing process of investment casting in the lost wax technology consists of a number of technological operations: preparing of wax models and their assembling in the model units, the preparation of ceramic mixture, successive layers of debris, wax melting in an autoclave, drying the samples at 100 °C, heating the samples at temperatures ranging from 400 to 700 °C. So far, the technology was based on the use of ceramic mixture, which the bond was hydrolysed ethyl silicate. Currently, due to environmental protection and improvement of working conditions, more and more binders with alcohol is replaced with an aqueous solution of colloidal silica. In the study, as the basic of individual layers a ceramic form, used regenerated ceramic mixture derived from foundry and green ingredients. Used ceramic moulds after mechanical reclamation was given to sieve analysis to determine the grain size (dL). Grain sizes 0.2, 0.4 and 0.63 mm were used for the coating of ceramic moulds. The paper presents results of research aimed at the determination of the relationship between tensile wet strength and grain size of ceramic mould: Rm =f(dL). Tests were conducted on cylindrical samples, which deposited a layer of reclaimed ceramic material.

21402 Al-4.0wt%Cu合金の凝固挙動に及ぼす鋳型寸法の影響(一般講演 アルミニウム材)

The influence of mold size on the solidification structure was examined. The cylindrical mold made of alumina filled with Al-4wt%Cu alloy was subjected to the steady temperature gradient to obtain the stationary solid-liquid interface, and then the furnace was cooled. At required elapsed times, the mold was quenched in water. As a result, the curvature of the solid-liquid interface was decreased with decreasing diameter of the mold. And, it was found that the solidification started 20 to 30 second after cooling of the furnace.

Improved expressions for field values of compaction test parameters

In most compaction test procedures, depending on the size of the compaction mould, a fraction of the soil sample with particle sizes larger than a specific value is discarded. This fact limits the use of laboratory values of compaction test parameters, namely the optimum moisture content and the maximum dry unit weight, for field compaction of soils. This technical note provides improved expressions for determining the optimum moisture content and the maximum dry unit weight of field soil samples on the basis of laboratory compaction test results, which do not consider the larger particles of the field soil samples. The improved expressions would be useful for earthworks, and for developing standards for compaction tests for field applications.

W-M(M=Cu, Sn, Ni)계 고밀도 복합재료 제조에 관한 기초연구(I)

For the purpose of obtaining basic information on the development of lead-free materials, a high density composites (a) W-Cu, (b) W-Sn (c)W-Cu-Sn and (d) W-Cu-Ni were fabricated by the P/M method. The particle size of used metal powders were under 325 mesh, inner size of compaction mould was <TEX>$\phi8$</TEX> mm, and compaction pressure was 400 MPa. A High density composite samples were sintered at a temperature between <TEX>$140^{\circ}C$</TEX> and <TEX>$1050^{\circ}C$</TEX> for 1 hour under Ar atmosphere. The microstructure, phase transformation and physical properties of the sintered samples were investigated. As the results, the highest relative density of 95.86% (10.87 g/<TEX>$cm^3$</TEX>) was obtained particularly in the sintered W-Cu-Sn ternary system sample sintered at 450 for 1hr. And, Rockwell hardness (HRB) of 70.0 was obtained in this system.

The effects of manganese content and mould size on abrasion and slurry erosion behaviour of chromium–manganese iron systems investigated by positron lifetime spectroscopy

Abrasion and slurry erosion behaviour of chromium–manganese iron samples with chromium (Cr) in the range ∼16–19% and manganese (Mn) at 5 and 10% levels have been characterized for hardness followed by microstructural examination using optical and scanning electron microscopy. Positron lifetime studies have been conducted to understand the defects/microporosity influence on the microstructure. The samples were heat treated and characterized to understand the structural transformations in the matrix. The data reveals that hardness decreased with increase in Mn content from 5 to 10% in the first instance and then increase in the section size in the other case, irrespective of the sample conditions. The abrasion and slurry erosion losses show increase with increase in the section size as well as with increase in Mn content. The positron results show that as hardness increases from as-cast to heat treated sample, the positron trapping rate and hence defect concentration showed opposite trend as expected. So a good correlation between defects concentration and the hardness has been observed. These findings also corroborate well with the microstructural features obtained from optical and scanning electron microscopy.

Production and properties of copper-based powder antifriction material

The paper examines how temperature and strain rate influence the deformation of a porous powder billet made of an antifriction material. Copper and nickel-based alloy powders produced from industrial waste are used as the initial material. The ultimate strain in compression is established and used to calculate the mold sizes in tool development. Ambiguous temperature dependence of the mechanical and antifriction properties is obtained. Temperature and strain rate that ensure satisfactory mechanical and antifriction properties are found. Processes for producing parts from the antifriction material are proposed.

Preparation and cell affinity of microtubular orientation-structured PLGA(70/30) blood vessel scaffold

In this study, a kind of microtubular orientation-structured blood vessel mimicking natural structure was fabricated with poly(lactide- co-glycolide)(70/30) (PLGA(70/30)) solutions in 1,4-dioxane by an improved thermal-induced phase separation (TIPS) technique. The effect of main factors of the TIPS technique, such as environmental temperature, temperature gradient and concentration of the polymer solution on the structure and morphology of formed vessel scaffold was investigated. It was observed that the outer-wall of the scaffold became thick obviously and the microtubules neighboring the outer-wall became disordered with environmental temperature increasing. The diameter of microtubules of vessel scaffolds reduced with temperature gradient increasing or concentration of the polymer solution increasing. By controlling parameters of the TIPS, the scaffolds with various morphologies could be manufactured, which had different diameters of microtubules. On the other hand, inner-diameter and outer-diameter of the vessel scaffolds could be controlled by adjusting size of the polyethylene mould. Cell affinity of the scaffolds was tested in vitro by using A10 cell as model cells. Results showed that the cells grew well in the vessel scaffolds which were modified by ammonia plasma treatment and then anchored with collagen. The cells could array along the direction of the microtubules.

Effect of Gravel Size, Type, and Mold Size on the Carrying Capacity of Calcareous Fines-Gravel Mixes

Calcareous soils are used as graded base course materials in the Eastern Province of Saudi Arabia. The specimens tested in the laboratory are different from those in the field because of the removal of the oversize particles. The effects of maximum aggregate size on the load carrying capacity of calcareous fines (marl)-gravel mixture were studied. A large-size mold that can accommodate particles up to 50.8 mm was used to study the effect of oversize particles. Limestone aggregates (LSA) and steel slag aggregates (SSA) were used. The results indicate that the California bearing ratio (CBR) and the Clegg impact value (CIV) increase with the increase in the maximum aggregate size. The increase in the CBR values can reach 19% when the maximum aggregate size was increased from 19.05 to 50.8 mm. The CBR values for the calcareous fines-SSA mixtures were greater than those for the calcareous fines-LSA mixtures by up to 24%. The conventional CBR mold overestimates the CBR values by up to 43%. The results also clearly indicate the strong correlation between the CBR and the CIV results.

Flow Dynamics in Thin Slab Molds Driven by Sustainable Oscillating Jets from the Feeding SEN

Sustainable oscillations of discharging jets from a two-port SEN in a thin slab caster were studied using various experimental water-modeling techniques and mathematical simulations via a combination of Reynolds Stress Model and Volume of Fluid Model to follow interface dynamics of liquid phase. A dynamic distortion of low frequency was observed on fluid flow. This distortion enhances the permanent oscillations of discharging jets and finally produces large gradients of Reynolds stresses at their boundaries with the surrounding flow. Thus high strain stresses derive into large gradients of dissipation rates of kinetic energy through the jets giving place to large and small eddies which transport energy to the free bath surface and refine the flow structure located below the tip of the SEN, respectively. As a final result non-symmetric flows with high meniscus instability are produced independently of casting speed and mold size. These results are a bottom line reference to design future SEN's for thin slab casters with improved performances.

Anterior and Posterior Cartilage Graft Dimensions in Successful Laryngotracheal Reconstruction

To describe the dimensions of cartilage grafts used for successful laryngotracheal reconstruction, with the goal of establishing appropriate sizes for "off-the-shelf" tissue-engineered cartilage grafts. A retrospective review of prospectively maintained operative illustrations of a single surgeon's experience. Two tertiary children's hospitals. A consecutive sample of 54 patients (tracheotomized or intubated) with a diagnosis of subglottic stenosis. Each patient underwent anterior (n = 30), posterior (n = 3), or anterior and posterior (n = 22) laryngotracheal reconstruction. Rib cartilage was used in 51 patients and thyroid cartilage was used in 3 patients. Successful or failed extubation. Of the 54 patients, 48 (89%) were successfully decannulated. The mean +/- SEM length of the anterior graft was 20.7 +/- 10.3 mm, and the mean width of the anterior graft was 7.7 +/- 2.5 mm. The mean length of the posterior graft was 13.9 +/- 2.9 mm, and the mean width of the posterior graft was 4.2 +/- 0.9 mm. With the prospect of tissue-engineered cartilage implants becoming available for laryngotracheal reconstruction, the most appropriate templates for designing these implants should be based on the geometric dimensions of grafts carved from native tissues in cases that have been successfully decannulated. Based on our analysis, the use of 2-mm increments for the posterior grafts suggests a set of molds that are 2, 4, and 6 mm wide and 22 mm long. Using 2 x 2-mm increments for the anterior grafts indicates that 36 mold sizes will be sufficient for 90% of predicted cases.

Cell Morphology and Mechanical Properties of Rigid Polyurethane Foam

Polyurethane foam, used as a supporting or insulating material, is sometimes formed in complex molds with significant variations in geometry and size. This work investigates the relationships between cell morphology, density, and mechanical properties in a molded polyurethane material using relatively small cylindrical molds. Understanding these relationships will help mechanical designers to analyze and predict the responses of foam components accurately. Three mold sizes are used to study changes in cell morphology (cell area, cell diameter, aspect ratio, cell angle, cell edge length, cell face thickness, and cell edge thickness), density, and mechanical properties (Young’s modulus and collapse stress) with respect to position within the mold. The density is shown to increase from the top to the bottom of the reference mold but does not change significantly in the small and tall molds. However, the mechanical and cell morphology properties show more changes in the small and tall molds when compared to the reference mold even though there are only small changes in density.

Design of experiments for the qualification of EVA expansion characteristics

Ethylene vinyl acetate (EVA) is a highly utilised material for the manufacture of shoe soles and mid-soles due to its comfort, durability and UV stability. It is also used extensively for exercise mats, wall insulation and sports protection padding. The material can be manufactured into sheets by compression moulding or injection-moulding processes. This paper is concerned with research to gain knowledge of the behaviour of EVA during the injection moulding of shoe soles and shoe mid-soles. Though there is significant experience with the general use of EVA during the injection-moulding process this knowledge has been gained through years of experience and moulds are designed by a combination of the producer's knowledge and trial and error. With the increase in demand for customisation of mass-produced products a method for automating the design of moulds for expanding EVA products is highly desirable. When mixed with a suitable blowing agent, EVA has the remarkable ability to expand between 30% and 90% compared to the injection mould size, depending on the amount of blowing agent added. However, EVA does not expand uniformly and currently there is no precise method of predicting the expansion of components with variable thickness. This paper presents a methodology for determining the expansion characteristics of EVA coupled with results relating to the initial findings for material expansion to enable the design of a method for automatically generating mould cavity geometry.

Temperature and Mold Size Effects on Physical and Mechanical Properties of a Polyurethane Foam

Rigid polyurethane foams are used as thermal or vibration insulators and energy absorption material, and are often molded directly in place, where a smooth, thin skin forms between the mold and the cellular structure. Density gradients and the presence of a skin are known to affect the mechanical properties of the foam. We investigate the effect of processing temperature (25, 40, 65, and 85 C) and mold size (aluminum cylinders with diameters of 29, 41, and 51mm) on the average density and density gradients (radial and vertical) of a free-rise, water blown, rigid polyurethane foam system, and measure the effects on compressive modulus of elasticity and collapse stress. In general, both average density and radial density gradients decrease with increasing processing temperature and larger mold sizes. A reduction in average foam density corresponds with decreases in the elastic modulus and compressive strength. These mechanical properties are compared to reference samples extracted from very large batches of foam with a uniform density of 0.10 g/cc, where normalization of the compressive data shows the elastic modulus to exhibit the strongest dependence on processing temperature and mold size.

Effect of material internal pressure in curing process of SMC roll forming

Sheet molding compound (SMC) is applied to mass-production of FRP. SMC is usually formed in compression molding. However, this molding method needs huge forming energy and is not suited for long-sized products by restriction of mold sizes. So I have attempted to apply roll forming, which is known as metal rolling, to SMC. SMC roll forming has many advantages compared with other molding method, for instance the lower forming energy, and the short production time. The SMC roll forming method has two procedures of the forming process and the curing process. Now, the curing oven of the batch type of the boxy shape is used for the curing process. But, it is not suitable for continuous curing system, because of rising of the material internal pressure.In the present research, in order to develop and design the curing system applied the roll-shaped curing oven, the expansion history of the specimens caused by the material internal pressure in curing was investigated in detail.

Pressure Behavior of the Mold Cavity in a Differential Pressure Casting Unit with Two Chambers -Influence of Mold Temperature, Mold Size and Crucible Conditions-

Pressure Behavior of the Mold Cavity in a Differential Pressure Casting Unit with Two Chambers -Influence of Mold Temperature, Mold Size and Crucible Conditions-

Improvement of bloom casting and high reduction breakdown process

In May 1998, Muroran Works installed a near-net shape casting and compact high reduction (NCR) process in its steelmaking plant. The No.3 continuous casting machine was rearranged to cast middle cross section blooms, and a reheating furnace and a 2-passes high reduction breakdown mill were newly equipped. No.3 CCM casts square 220 mm mould size blooms and the breakdown mill reduces their cross section to square 162 mm. This combined process improved the quality of the cast billets and achieved high productivity.

Effects of fiber length and volume fraction on the reinforcement of calcium phosphate cement.

A self-setting calcium phosphate cement (CPC) transforms into solid hydroxyapatite during setting at body temperature, and has been used in a number of medical and dental procedures. However, the inferior mechanical properties of CPC prohibits its use in unsupported defects, stress-bearing locations or reconstruction of thin bones. The aim of the present study was to strengthen CPC with fiber reinforcement, to examine the effect of fiber length and volume fraction, and to investigate the reinforcement mechanisms. Previous studies employed either short fibers for random distributions, or continuous fibers that were as long as the specimen size with preferred orientations such as unidirectional alignment. In the present study, a novel methodology was developed in which fibers several times longer than the specimen mold size were randomly mixed with the CPC paste to approximate the isotropy associated with short fibers, and at the same time achieve the high reinforcement efficacy associated with continuous fibers. Carbon fibers of 8 microm diameter were used with fiber lengths ranging from 3 mm to 200 mm, and fiber volume fraction from 1.9% to 9.5%. A three-point flexural test was used to fracture the specimens. Scanning electron microscopy was used to examine crack-fiber interactions and specimen fracture surfaces. The composite containing fibers of 75 mm in length at a volume fraction of 5.7% achieved a flexural strength about 4 times, and work-of-fracture 100 times, greater than the unreinforced CPC. It is concluded that randomly mixing the CPC paste with carbon fibers that were several times longer than the specimen mold size resulted in substantial improvements in strength and fracture resistance; the reinforcement mechanisms were crack bridging and fiber pullout; and fiber length and volume fraction were key microstructural parameters that determined the cement properties.

Effects of Calcium Sulfate on Swelling Potential of an Expansive Clay

Abstract The unique chemical features of calcium sulfate are largely manifested by its phase transformation due to the reversible hydration-dehydration reaction. Due to the harsh climatic and environmental conditions in eastern Saudi Arabia, such phase changes add to the potential swelling hazards of local expansive clays. The adsorption of water by expansive soils and the hydration of anhydrite to gypsum are the sources of much damage to foundations throughout the world. This paper attempts to assess the swelling caused by the interaction of calcium sulfate phases, especially gypsum and anhydrite, with expansive clay. Such assessment was primarily based on studying the geotechnical, mineralogical, and volume change characteristics of calcium sulfate-bearing soils. X-ray and thermal analyses were used to estimate the type and amount of minerals during phase transformation of calcium sulfate. The swelling potential was determined using an improved version of the simple odometer and constant-volume tests. The conventional odometer is the device usually used in these tests. However, the size of soil samples, the complete confinement, and the rigidity of the conventional odometer imposes a serious limitation on the application of the laboratory results to actual field problems. Therefore, the authors investigated the use of a large-scale odometer with different mold sizes and shapes on the swelling potential of some mixtures of expansive clay and calcium sulfate phases. In addition, the soil fabric of these mixtures was investigated using scanning electron microscopy to explain the volume change behavior. The results of this investigation indicated that the swelling potential of clay-calcium sulfate mixtures decreased as the percentage of calcium sulfate was increased, and this reduction was more pronounced when gypsum was used. Swelling pressure was observed to be the highest in the conventional odometer and lowest in the large-scale square odometer mold.