Hitachi Metals, Ltd.

Honda Giken Kogyo K.k.

501 Hitachi Metals, Ltd.

Fumio Obata

Hideaki Nagayoshi

Makoto Suenaga

Toshiaki Tanaka

Jun Sakai

Kiyoshi Suehara

Hisashi Yasuda

Toshiki Yoshida

Takashi Kawai

Takeshi Natsume

Kouhei Imanishi

Ryoji Takahashi

Michio Makino

Yoshimi Kubo

Eiji Nakano

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 spheroidal graphite cast iron article having a thin portion and a thick portion, the number of spheroidal graphite particles having a diameter of 2 .mu.m or more being 600 /mm.sup.2 or more and less than 2000 /mm.sup.2 in the thin portion and 130 /mm.sup.2 or more and less than 600 /mm.sup.2 in the thick portion, and spheroidization percentage being 70% or more in the thick portion, is produced by a method comprising the steps of: (a) preparing an iron-base alloy melt having a composition consisting essentially by weight of 3.0-4.0% of C, 0.8-1.7% of Si, 1.0% or less of Mn, 0.2% or less of P, 0.01-0.2% of S, the balance being substantially Fe and inevitable impurities; (b) desulfurizing the iron-base alloy melt to control the sulfur content of the melt to less that 0.01% by weight; (c) adding a sulfur-containing material to the melt in such an amount that the sulfur content of the melt becomes 0.011-0.03% by weight; and (d) adding an Mg-containing material and a lanthanide element to the melt to conduct a spheroidizing treatment.

Method of producing spheroidal graphite cast iron article

Spheroidal graphite cast iron containing 0.016-0.030 weight % of S, in which the number of spheroidal graphite particles having a diameter of 2 .mu.m or more is such that it is 1700/mm.sup.2 or more when an as-cast iron portion measured has a thickness of 3 mm. This cast iron is produced by:

Spheroidal graphite cast iron

A thin high-strength article of spheroidal graphite cast iron having graphite particles dispersed in a ferrite matrix containing 10% or less of pearlite, characterized in that there are substantially no fine gaps between the graphite particles and the ferrite matrix. It is produced by pouring a melt having a spheroidal graphite cast iron composition into a casting mold; removing the casting mold by shake-out, while substantially the entire portion of the resulting cast iron product is still at a temperature of its A.sub.3 transformation point or higher; immediately introducing the cast iron product into a uniform temperature zone of a continuous furnace kept at a temperature of the A.sub.3 transformation point or higher, where the cast iron product is held for 30 minutes or less to decompose cementite contained in the matrix; and transferring the cast iron product into a cooling zone of the continuous furnace to cool the cast iron product at such a cooling speed as to achieve the ferritization of the matrix.

Thin high-strength article of spheroidal graphite cast iron and method

Conventionally, heat treatment was necessary in the final stage of producing nodular cast iron products to give the nodular cast iron with desired mechanical properties. This was necessary because of the loss of graphitization capability of the molten metal when it is being formed into nodular cast iron during the process of spheroidization, and the heat treatment is therefore required to decompose cementite formation and thereby promote graphitization. The process of producing nodular cast iron according to the present invention can achieve the promotion of graphitization and the increase in the number of graphite nodules, which are both important for the production of high-quality thin-shell cast iron products, through the synergetic effect of processing the molten metal with a graphitization agent such as SiC or CaC.sub.2 and of adding a graphite atomization agent such as Bi. The nodular cast iron produced by the process of the present invention can be made into thin-shell products which are provided with favorable mechanical properties either without any heat treatment or at most with low-temperature heat treatment.

Process of producing nodular cast iron

A brake member integrally cast from a single melt and composed of a sliding portion and a hub portion, the sliding portion having a flaky graphite cast iron microstructure with a good damping capacity and the hub portion having a high-strength cast iron microstructure. The sliding portion which may be a drum or a rotor has a damping capacity Q.sup.-1 of higher than 16.times.10.sup.-3. It is manufactured by pouring a melt having a hyper-eutectic flaky graphite cast iron composition into a cavity of a sand mold in which a chiller is embedded adjacent to a cavity region for the hub portion.

Brake member and method of manufacturing same

A cast iron melting process comprising the steps of charging recarburizer in the lower portion of an electric arc furnace, charging iron scraps, and charging oxidizing slag-forming agents and/or sponge irons, and/or blowing oxygen therein to make oxidizing slag, whereby a recarburizing reaction of an iron melt with the recarburizer is carried out in parallel with an oxidizing reaction of an iron melt with an oxidizing slag, thereby minimizing the loss of C and Si, while improving a recarburizing yield, with the resulting improvements in economy.

Growing community of inventors

Kitakyusyu, Japan

Fumio Obata