JPS59157221A - Manufacture of spheroidal graphite cast iron - Google Patents

Abstract

PURPOSE:To shorten the working stage and to reduce the manufacturing cost by rapidly cooling a casting from a temp. above the A1 transformation point at a cooling rate at which pearlitic transformation is not caused, holding the casting at a temp. at which a mixed structure consisting of bainite and austenite is stably formed for a prescribed time, and cooling the casting. CONSTITUTION:Molten metal having the composition of spheroidal graphite cast iron is charged into a casting mold and solidified. The resulting casting is taken out of the mold at 850-900 deg.C which is above the A1 transformation point. The casting is rapidly cooled from 850-900 deg.C at a cooling rate at which pearlitic transformation is not caused, and it is held at a temp. at which a mixed structure consisting of bainite and austenite is stably formed for about 2hr. The casting is then allowed to cool or cooled with water.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-strength spheroidal graphite cast iron, and particularly relates to a method for producing spheroidal graphite cast iron that has high strength and high toughness in an as-cast state.

Among the cast iron materials, spheroidal graphite cast iron is the most durable. However, its tensile strength is at most a level of BOkg/Tomo 2, so it is necessary to cast specially refined materials, reheat, quench and temper, or to
It is extremely difficult to obtain spheroidal graphite cast iron with high strength and high toughness unless it is subjected to an austempering treatment as disclosed in Japanese Patent No. 3-48014.

In other words, reheating a cast product that has been cooled once after it has been removed from the mold for heat treatment naturally requires a large amount of thermal energy, which not only increases production costs but is also undesirable from an energy conservation standpoint. It is.

Furthermore, in order to stably obtain high strength and high toughness in the as-cast state, large amounts of expensive special elements such as Ni, MO, and Qu must be added, which is extremely uneconomical.

Therefore, recently, during the cooling process from the completion of solidification to the completion of A1 transformation, the @-type is exposed to mold removal as soon as possible after the completion of solidification to rapidly cool it and increase the amount of pearlite in the matrix structure. , technologies are being developed to improve mechanical properties.

Even in this platform, a considerable amount of pearlite stabilizing elements such as Mn, Sn, On, etc. must be added, and high strength and toughness that can replace forged materials cannot be obtained, so it is not necessarily a preferable method. Therefore, the present inventors developed a new technique to obtain the desired structure by adjusting the sinking speed after pouring without adding large amounts of special elements.
・It was uttered. - An object of the present invention is to provide a method for manufacturing high-strength, high-toughness spheroidal graphite cast iron that can shorten the length of the workpiece and reduce manufacturing costs.

Embodiments of the present invention will be described in detail below.

A method for manufacturing spheroidal graphite cast iron in which a molten metal having a composition of spheroidal graphite cast iron is placed in a mold and solidified, and then the cast product is removed from the mold at a constant temperature of A1 or higher and rapidly cooled. The mixture of bainite and sub-stenite is rapidly cooled at a temperature that does not cause pearlite transformation at a temperature higher than the Al transformation point, and is maintained at a temperature that allows stable formation of a mixture of bainite and sub-stenite. It is something that is cooled or rapidly cooled.

Example 1 (2) Test piece φ40　X　300〜 (3) Injection temperature 1400~1420°0 (4) Heat treatment (6) Organization As shown in FIG.

Example 2 (1) Ihigaku component (N wind%) (2) Test piece φ40 x 300 (3) Injection temperature 1400~14200C (4) Heat treatment 1゜ ψcold (5) Mechanical properties (6) Organization As shown in FIG.

) Example 3 (1) Chemical composition (vehicle volume%) (2) Test piece φ40X300 fight (3) Injection temperature 1400～14go’b (4) Heat treatment (5) Mechanical properties (6) Organization As shown in Figure 83.

As mentioned above, the matrix structure is a bainite structure, and spheroidal graphite cast iron can be obtained which has extremely good mechanical properties such as tensile strength, yield strength, strength, and 'ffi impact value.

As is clear from the above explanation, the method for producing spheroidal graphite cast iron according to the present invention involves rapidly cooling a cast product from a temperature above the A1 transformation point at a cooling rate that does not cause pearlite transformation, thereby stabilizing the 11-structure of bainite and austenite. It is maintained at a temperature that causes a certain amount of heat, and after a predetermined period of time has elapsed, it is allowed to cool or is rapidly cooled.

Therefore, we were concerned about economic efficiency, such as shortening the manufacturing process of cast products and reducing manufacturing costs by eliminating reheating, but we were able to stably manufacture spheroidal black ship cast iron, which has extremely excellent mechanical properties such as high strength and high toughness. It is possible.

A little glare I'm Haruka , 10:3

Claims (1)

[Claims] A method for producing spheroidal graphite cast iron, in which a molten metal having compacted spheroidal graphite cast iron is poured into a mold and solidified, and then the cast product is taken out of the mold at a predetermined temperature higher than the Al transformation point and rapidly cooled.
It is characterized by rapidly cooling from a temperature above the transformation point at a cooling rate that does not cause pearlite transformation, maintaining the mixture structure of bainite and austenite in a stable state, and cooling it naturally or rapidly after a predetermined period of time has elapsed. A manufacturing method for spheroidal graphite cast iron.