Toughening of Ceramic Shell Mould with Rice Husk Fiber (CSm-RH) to Improve Strength Property and Mould Performance

For ages, ceramic shell mould (CSm) have been extensively applied in investment casting industry. The formation of CSm requires multiple steps of dipping, layering drying and firing stages. The later steps are very crucial as the solidification thin layer CSm that consist of loose ceramic particles easily cracks when exposed to the higher thermal effect. The inclusion of fiber or any reinforces phases is able to enhance fired ceramic body and also strengthen the green ceramic structure. Thus, the feasibility of rougher NaOH treated rice husk fiber (RHT) prior embedded into composited structure has shown a significant CSm improvement by induced a better adhesion properties and larger bonding area with brittle ceramic matrix, resulted in increased green strength (1.34 MPa) and fired body strength (4.32 MPa). Owing to the decomposed of lignin layer in CSm with untreated rice husk fiber (CSm-RHU) exhibited a higher porosity that provide a better permeation paths of air flow during molten metal pouring as increased 30 % from the standard CSm permeability, giving an enormous benefit for investment casting cooling process. Overall, the incorporation of RHT fiber in a CSm matrix of both green and fired body governed in toughening of brittle ceramic body, hence avoid failure to the casting mould.

Effect of Pouring Temperature and Heating of Ceramic Shells Mould on Projection of Thin Wall Castings

One of the research directions of this study is to determine the possibility of making precise, thin-walled castings from selected iron alloys. The scope of research work is aimed at determining the applicability of the casting process of selected iron alloys with the technology of wax pattern, for making precise castings with a wall thickness of less than 3 mm. The article presents the results of tests carried out for experimental castings with the shape of steps, characterized by different wall thicknesses: 1 mm, 5 mm, 10 mm, 25 mm. The castings were made of LH14, Gs42crMo4, L35H7MP2, LH26N9, 316L cast steel, and a new alloy marked “0”. The metal was smelted in an induction furnace with a capacity of 150 kg. The technology of ceramic shell mould used in the plant was used to make the experimental castings. Ceramic shell moulds were heated in a chamber furnace at a fixed temperature. The time of annealing the ceramic mould was constant in a ceramic form. The following parameters were variable during the tests: iron alloy, pouring temperature, and annealing temperature of the ceramic shell mould.

Fabrication of Ceramic Moulds Using Recycled Shell Powder and Sand with Geopolymer Technology in Investment Casting

Lost-wax casting, also called precision casting, is the process of casting a duplicate metal sculpture cast an original sculpture. The ceramic shell mould used in lost-wax casting usually consists of several layers formed with fine zircon and granular mullite particles using silica gel as a binder. However, it is a complicated and time-consuming process. Large amounts of waste moulds that need to be disposed and recycled become an environmental concern. In this study, waste shell sand from the recycled mould and calcium carbonate/metakaolin were used as raw materials to prepare geopolymer slurry and coating. The influence of mixing ratio and the SiO2/K2O modulus of the alkali solution on the setting time and green/fired strength were evaluated. Ceramic shells with one to four layers of geopolymer slurry and waste sand sprinkling were fabricated and tested for their permeability and green/fired strength. It was found that geopolymer shells had higher green/fired strength and better permeability than the original zircon/mullite shell. For foundry practice, metal casts were fabricated using recycled ceramic shell moulds with one to four layers of geopolymer coating. All cast results have their dimensions all within tolerance limitation and up to 13 h can be saved for the preparation of shell moulds.

Achieving environmental sustainability in the shell mould foundry through thermal reclamation

Shell moulding is a process for producing simple or complex near-net-shape castings and maintaining tight tolerances with a high degree of dimensional stability. The main objective of the present research is to achieve environmental sustainability by thermal reclamation of the used shell mould foundry sand and present the results of achieving environmental sustainability. The investigations indicate that the thermal reclamation of the used foundry sand helps in achieving sustainability, and the selection of optimal process parameters like percentage of resin, catalyst, and fresh silica sand addition are very important in the shell mould foundry.