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A copper alloy powder composed of Cu-14Ni-3Si-2V-2Cr-1.5Fe-1Al-0.5P has been developed for application to laser-clad valve seats. Laser-clad valve seats offer several advantages such as higher engine output and improved fuel economy owing to lower valve head temperature and an increased intake throat diameter compared with conventional press-fit valve inserts made of ferro-based powder metal. Previously, a material having a principal chemical composition of Cu-12Ni-10Co-3Si-2V-2Nb-1.5Fe-1Al was developed to obtain large hard intermetallic compounds. The microstructure of this material is formed by a two-liquid separation reaction, which has been applied to powders of different chemical compositions for laser-clad valve seats of production engines. Although this material shows superior valve seat wear resistance, it has certain drawbacks, including the high cost of the powder, high probability of microcrack formation and low machinability of the laser-clad layer.

A linear-shaped module based on Si-Ge alloys has been made for thermoelectric generation. The module is designed for generating electricity by exhaust heat of, e.g., plants, furnaces or automobiles. The module consists of 9 couples of p- and n-type Si-Ge alloy-based thermoelectric semiconductors. Carbon layers are made on both sides of the p- and n-type elements, and then the elements are electrically connected in series using Mo electrodes by blazing method. The size of the module is approximately 3.5 mm in width, 70 mm in length and 9.3 mm in height. Maximum power of the module was 2.0 W at a temperature difference of 509 K between the hot and cold sides of the module. A variation of generating power was measured for 150 modules. Maximum power of every module-block consisting of 10 modules was evaluated at a temperature difference of 400 K. The maximum power of the module-blocks was varied from 6.9 W to 8.7 W.

JIS SCM440M (SAE4140H), heat treated to the strength level of 120 to 140 kgf/mm2(171 to 199 ksi) -ISO 12.9 class-, is currently used for cylinder head bolts of Japanese passenger cars. Lower alloy steels, such as SAE 1541 for example, have not been substituted for JIS SCM440H so far because of their high susceptibility to delayed fracture. Daido Steel has tackled this problem and succeeded in applying the lower alloy SAE 1541 steel to 12.9 class cylinder head bolts by enhancing the resistance to delayed fracture by reducing impurities, especially sulphur. In this paper mechanical properties and delayed fracture characteristics of SAE 1541-ULS (Ultra Low Sulphur) steel are reported. 1541-ULS (S<0.005%, S+P< 0.020%) shows outstanding resistance to delayed fracture compared to conventional steel. Furthermore, the amount of MnS inclusions decreases remarkably in ULS steel, which results in high toughness.

Excellent fuel economy and high performance have been urgent in Japanese automobile industries. With increasing engine power, many of the power train components have to withstand higher loads. Differential pinion gear being one of those highly stressed parts, excellent fatigue and shock resistance have been demanded. At first the fundamental study on the fatigue and impact crack behavior of carburized components was studied and the new grade composed of 0.18%C-0.7%Mn-1.0%Cr-0.4%Mo was alloy designed. Furthermore, Si and P is reduced less than 0.15 and 0.015%, respectively aiming at the reduction of intergranular oxidation and improved case toughness. The differential gear assembly test has proved that the new grade shows three times as high impact strength as that of conventional steel, SCM418, and almost the same as that of SNCM420 containing 1.8%Ni.

Experiments were conducted with 4-cylinder and single-cylinder direct injection diesel engines to examine the effects of combustion chamber insulation on heat rejection and thermal efficiency. The combustion chamber was insulated by using a silicon nitride piston cavity that was shrink-fitted into a titanium alloy crown. The effect of insulation on heat rejection was examined on the basis of heat release calculations made from cylinder pressure time histories. High-speed photography was used to investigate combustion phenomena. The results showed that heat rejection was influenced by the combustion chamber geometry and swirl ratio and that it was reduced by insulating the combustion chamber. However, because combustion deteriorated, it was not possible to obtain an improvement in thermal efficiency equivalent to the reduction in heat rejection.

This study concerns a dissimilar materials joining technique for aluminum (Al) alloys and steel for the purpose of reducing the vehicle body weight. The tough oxide layer on the Al alloy surface and the ability to control the Fe-Al intermetallic compound (IMC) thickness are issues that have so far complicated the joining of Al alloys and steel. Removing the oxide layer has required a high heat input, resulting in the formation of a thick Fe-Al IMC layer at the joint interface, making it impossible to obtain satisfactory joint strength. To avoid that problem, we propose a unique joining concept that removes the oxide layer at low temperature by using the eutectic reaction between Al in the Al alloy and zinc (Zn) in the coating on galvanized steel (GI) and galvannealed steel (GA). This makes it possible to form a thin, uniform Fe-Al IMC layer at the joint interface. Welded joints of dissimilar materials require anticorrosion performance against electrochemical corrosion.

Hypereutectic Al-Si alloy 390, containing large amounts of hard silicon particles, has mainly been used for wear-resistant alloy applications. In the case of hypereutectic Al-Si alloys, the primary silicon particle size and distribution must be controlled to obtain stable wear resistance. The service life of furnaces and molds is shortened by the high melting and casting temperatures required for controlling primary silicon. Furthermore, machinability is degraded by large primary silicon particles. To overcome these problems, a new wear-resistant Al-Si alloy has been developed which provides good castability and machinability. This alloy also has wear resistance and mechanical properties similar to those of the 390 alloy. Specifically, the problems regarding castability and machinability were solved by decreasing the silicon content of the 390 alloy, but that also reduced wear resistance.

Improving the impact strength of the differential gears is one way to reduce the size and weight of the final drive unit. Previously, we developed high-strength steel for gear use by adding molybdenum and reducing impurities such as phosphorus and sulfur. However, additional improvement of impact strength is required these days due to higher engine torque and demands for further weight reductions. Toward that end, we focused on boron, which has been used as an element for improving hardenability, and analyzed what effect its addition would have on impact strength. Useful knowledge was obtained for improving impact strength through enhancement of grain boundary toughness. Various steels were then produced experimentally and used in gear strength tests. The results made it possible to improve impact strength while reducing the content of other alloys, resulting in the development of a chromium-molybdenum-boron case hardening steel with superior cold forgeabilty.

Various heat resistant alloys are being introduced for use in automobile emission equipment, such as thermal reactors and catalytic converters. For the past several years Japan has been developing alloys which emphasize oxidation resistance. Therefore, oxidation phenomena have been thoroughly researched and clarified. On the other hand, embrittlement, which is a marked deterioration similar to oxide deterioration, has not been studied sufficiently. The major subjects of investigation were the two forms of embrittlement in austenitic heat resistant alloys, caused by the precipitation of σ phase and the absorption of Nitrogen. Useful information was obtained from these results.