Ryobi is very active in the development of die cast aluminum composites for wear applications. Although these materials are of great interest, there are several negative features: high production costs, machinability, recycling, and high materials cost (e.g., carbon fibers). Composites have interesting and appropriate uses in applications where creep strength and heat resistance are critical. Ryobi managers expressed the belief that automotive engineers will specify that cylinder liners be produced from composite materials in the future. Brake components are another possible application. They have developed the RX 1000 metal matrix composite materials for die casting operations, which are described in Table 3.1.
Ryobi's managers take the view that squeeze casting may be better than die casting for higher performance components, even though squeeze casting is more expensive. At present Ryobi is producing wheels, cross members, and certain components for high performance cars like the Mazda RX7 by squeeze casting.
Kubota Corp.'s New Materials Group currently has two major initiatives: process technologies and materials technologies. The process technologies deal with hot isostatic pressing (HIP) and cold isostatic pressing (CIP). The materials technologies deal with issues like corrosion resistance, heat resistance needs, and creation of new businesses. The R&D group is integrated with manufacturing, marketing, sales, and business development.
Kubota has excellent capabilities in HIP, CIP, and sintering. Its HIP machine used for silicon nitride production is one of the largest of its kind in the world. The largest HIP product they have produced is a ceramic component 500 mm in diameter and having a wall thickness of 50 mm. Kubota claims this product is the largest of its kind ever produced in the world.
Kubota manufactures cylinders for extrusion machinery that are produced from rapidly solidified powders, which are then bonded using HIP. These have enhanced corrosion and impact resistance for plastic extrusion machinery.
Kubota is using a HIPed chromium matrix alloy to produce skid buttons that are used by the steel industry to support reheated slabs. The new skid buttons are said to have four times more wear resistant than those of heat resistant steel. This new alloy is anti-oxidizing and can be utilized at temperatures in the vicinity of 1350°C. Kubota is supplying skid buttons to most of the major steel producers of Japan, having manufactured over 4,000 pieces since 1988. Kubota has made a very intense effort in the development of ceramics for advanced die casting processes. Its ceramics are claimed to have higher strength, toughness, and corrosion resistance against molten aluminum compared to traditional ceramics used in the industry. Maximum dimensions of the Kubota ceramics for the die casting industry are 50 inches long, 20 inches in diameter, and 2 inches thick. Kubota engineers work very closely with end users and customers in producing state-of-the-art ceramics for the die casting industry. They produce two kinds of materials for such applications: KN, a silicon nitride product, and MC, a composite material consisting of a titanium matrix containing ceramic particulates distributed throughout the matrix. Applications of the KN material in die casting include transfer ladles for Ube squeeze casting systems, transfer tubes for Toshiba electromagnetic pump systems, riser stalks for low pressure die casting, heater element tubes for holding furnaces, thermocouple protection tubes, nozzles, and a variety of other applications. Ceramic composites of the MC material are used as shot sleeves for high pressure aluminum die casting for both horizontal and vertical machines. The composites have very high insulation properties to die sleeves as well as high corrosion resistance to molten aluminum. The physical properties of the Kubota KN and MC materials for the foundry industry are presented in Table 3.2.
Kyocera is a well-established company in the field of ceramics. It has been active in the development of advanced ceramic products for use by the foundry industry. Its fine ceramic division produces a wide variety of materials: high purity alumina; silicon nitride (high reliability); silicon carbide (high wear, used in applications such as mechanical seals); zirconia (scissors, knives, watchbands); aluminum nitride (for high thermal conductivity applications); corderite; titania; and cermets. Kyocera's silicon nitride is based on proprietary technology. Silicon nitride stalk tubes developed for the low pressure permanent mold sector have demonstrated a 2 year life under proper conditions.
The products available from Kyocera at present for metal casting applications include ladles, die cast sleeves, stalks, thermocouple protection tubes, heater tubes, degassing pipes and rotors, fixtures for wetting processes, and pumps.
Kyocera produces two types of silicon nitride for use with molten aluminum. Table 3.3 presents typical properties of the Kyocera ceramics available to the foundry industry. Similarly desirable property levels cannot be achieved using ductile iron.
Asama Giken appears to be more active in the area of development than research. It is funding research at a local university to investigate uses for spent sand with no positive results thus far. Asama Giken engineers use the Komatsu finite element program SOLDIA to simulate solidification in order to optimize mold and gating designs. The software includes capabilities for heat and fluid flow, calculation of cooling rates, and application of the Niyama criteria for shrinkage. The program is run on a Sun workstation, and about 24 hours of running time are needed for each simulation run. In orders from Honda, all design data for exhaust manifolds are received in digital form on diskettes with no drawings.
A major development effort relates to the production of thin wall exhaust manifolds for Honda. Asama Giken has been successful in reducing the manifold thicknesses from 6 mm to 3 mm. However, the newest target is 2 mm. At this thickness Asama Giken engineers feel they have a practical limit of 4% Si in their ductile iron product using their present gravity methods. They indicated that about 5% Si would be needed to achieve property targets. As a result they indicated that the thinner manifold would have to be cast stainless steel because of improved thermal fatigue and oxidation and corrosion resistance, with serious competition from stamped 13% Cr steel.