Hitachi Metals, Ltd.

Hisashi Yasuda

Mitsuru Yano

Kenji Itoh

Masatoshi Nakamizo

Takashi Hattori

Hideaki Nagayoshi

Fumio Obata

Kiyoshi Suehara

Toshiki Yoshida

Kouhei Imanishi

The spheroidal graphite cast iron member having a surface layer portion mostly composed of a ferrite phase and having a thickness of at least 1 mm, and an inner portion composed of a pearlite phase and a ferrite phase, the surface layer portion having a ferritization ratio of 70% or more which is larger than that of the inner portion by at least about 15% is produced by (a) pouring a spheroidal graphite cast melt into a casting mold; (b) removing the casting mold by shake-out after the completion of solidification of the melt, while substantially the entire portion of the resulting cast iron product is still at a temperature of its A.sub.1 transformation point or higher; (c) when the temperature difference between the surface layer portion and the inner portion has become 40.degree.-60.degree. C., introducing the cast iron product into a uniform-temperature furnace kept at 750.degree.-900.degree. C., where the cast iron product is held for such a time period as to produce the surface layer portion having a ferritization ratio of 70% or more which is larger than that of the inner portion by at least about 15%; and (d) transferring the cast iron product into a cooling furnace to cool the cast iron product at a cooling speed of 15.degree.-100.degree. C./min.

Spheroidal graphite cast iron member having improved mechanical strength

A method of manufacturing a heat resistant member includes the step of designing the shape of the heat resistant member, including the substeps of estimating thermal stress of the heat resistant member by heating a model formed by a high-thermal expansion material which has a similar shape to the desired shape of the heat resistant member while the model is restrained and also while it is free. The high-thermal expansion material is different from the material of the member being modeled and has a thermal expansion coefficient greater than that of the material of the member being modeled. Additionally, the step of designing includes the substeps of measuring the strain of the model at each of a plurality of predetermined positions while the model is heated by strain gauges adhered to predetermined positions on the model, and calculating the stress at each predetermined position from the difference in measured strain values between the restraint state and the free state. Finally, the manufacturing method includes casting the heat resistant member to the designed shape.

Method of manufacturing a product by estimating thermal stress using a

A method of estimating a thermal stress of a heat-resistant member, part or the whole of which is to be heated to a high temperature, comprising heating a model formed by a high-thermal expansion material and having a shape similar to that of the heat-resistant member; and measuring a thermal strain of the model at each of predetermined positions by strain gauges adhered thereto.

Method of estimating the thermal stress of a heat-resistant member by

A model for measuring stress distribution constituted by a light, integral polyurethane foam having little unevenness in density, the polyurethane foam being at predetermined sites provided with undercoating layers, to each of which a resistance wire strain gauge is attached via an adhesive, each of the undercoating layers having a thickness of 50-300 .mu.m and being made of a material which is unreactive with, hardly penetrable into and softer than the polyurethane foam. The stress distribution measurement is conducted by supporting the polyurethane foam model by one or more support members at positions corresponding to the restraint sites of an actual metal member, and applying a load to the polyurethane foam model at a position corresponding to the site of the actual metal member to which a load is actually applied, thereby measuring a stress distribution in the polyurethane foam model under substantially the same restraint conditions as in the actual metal members.

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Kitakyusyu, Japan

Hisashi Yasuda