JPH0191956A - Method for casting spherical graphite cast iron casting - Google Patents

Abstract

PURPOSE:To improve the strength and fatigue strength of a product by loading the core having a through-hole on a mold and cooling the vicinity of the hollow hole of a casting by flowing a cooling medium in the through-hole of the core. CONSTITUTION:The cavity 7 of a product member 1 is formed by abutting upper and lower split faces 5a, 3a and the shell core 8 having a hollow hole is fitted by penetrating the center part thereof vertically. The metal made panel body 11 pressing the center part thereof is arranged and a molten metal is poured from a sprue 14 with feeding the pressurizing air for cooling from an air feeding port 16 to execute casting. Even after completion of casting the air for cooling is fed extending over the specified time. Since the cooling speed of the circumference of the hole 1a of a product is increased the spherical graphite particle of the product is refined. Both the strength and fatigue strength of the product are thus enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for casting spheroidal graphite iron castings having hollow holes.

[Prior art]

Conventionally, iron castings with hollow holes, such as the wheels and nocle parts that support the front and rear wheels of automobiles, are often cast from spheroidal graphite cast iron, and in this casting method, a solid core forming a hollow hole is set in a mold. After pouring the molten metal into the mold, it is cooled and solidified by natural heat radiation.

[Problem that the invention seeks to solve]

In the conventional manufacturing method of spheroidal graphite iron castings, after pouring the molten metal into the mold, the entire casting is generally cooled and solidified by natural heat radiation, and the cooling rate at this time is relatively small. There is. For example, when casting spherical graphite using a solid core in the hollow hole forming part of the above-mentioned knuckle member having a hollow hole, the cooling rate of the relatively thick walled part near the hollow hole is about 2.0°C/s. e c, and the particle size of spheroidal graphite is approximately 4
The size becomes 0 μm, and the fatigue strength of that part is approximately 26 kg.
/mm! becomes smaller.

As described above, since the cooling rate after casting is low, a fine spheroidal graphite metal structure cannot be obtained, resulting in low strength and fatigue strength. Bearings and shaft members are often press-fitted into the hollow holes of cast products, but the press-fitting load is very large, so there is a problem that clutching occurs during press-fitting.
Furthermore, since the particle size of spherical graphite is large, there is also the problem that machinability is poor when cutting or polishing hollow holes.

[Means for solving problems]

The method for casting spheroidal graphite iron castings according to the present invention is a casting method for casting spheroidal graphite iron castings having hollow holes.
A core having a through hole is used as the core forming the hollow hole, and after the core is set in a mold, at least after the molten metal is poured, a cooling fluid is supplied to the through hole of the core through the passage formed in the mold. is used to cool the area near the hollow hole of the casting.

[Effect]

In the method for casting spheroidal graphite iron castings according to the present invention,
Using a core with through-holes and a mold with cooling fluid passages, the core is placed in the mold so that the passages in the mold communicate with the through-holes in the core, and at least after the molten metal is poured, Since cooling fluid is flowed through the through holes to cool the area near the hollow hole of the casting, the cooling rate during solidification increases, and the cooling rate of the molten metal near the core is faster than that of other parts, resulting in the formation of graphite particles. Coarsening is suppressed, resulting in a metal Mi weave made of fine graphite particles and excellent in mechanical strength.

〔Effect of the invention〕

According to the method for casting spheroidal graphite iron castings according to the present invention, as explained above, at least after the molten metal is poured, the surrounding portion of the hollow hole is cooled by a simple method of flowing cooling fluid through the through hole of the core. Increase the speed to make graphite particles finer,
It is possible to increase the strength, fatigue strength, etc. of that part and improve machinability.

(Example〕 Embodiments of the present invention will be described below with reference to the drawings.

First, the casting to be cast by the method for casting spheroidal graphite iron castings according to the embodiment and the mold used in the casting method will be described.

This mold is for casting a knuckle member for supporting a rear wheel of an automobile having a hollow hole, and the knuckle member 1 is a component necessary for a rear wheel support mechanism as shown in FIG.
After casting, the spindle mounting hole 1a (hollow hole) is cut,
A steel spindle is press-fitted there.

A mold M for casting the knuckle member 1 using spheroidal graphite cast iron material is a lower mold mold (hereinafter referred to as lower mold) 3 placed on a metal surface plate 2 as shown in FIGS. 2 and 3. A mold frame 4 is provided on the outer periphery of the lower mold 3, and an upper mold 5 (hereinafter referred to as the upper mold) is placed on the lower mold 3. A mold frame 6 is provided on the outer periphery of the upper mold 5, and a weight 11 is placed on the upper surface of the upper mold 5.

After combining the lower mold 3 and upper mold 5, both mold flasks 4 and 6 are assembled.
are connected with bolts and nuts.

To explain the structure of the upper mold 5 and lower mold 3, the lower mold 3
A cavity 7a for half of the knuckle member 1 is recessed approximately in the center of the split surface 3a, and a cavity 7b for the remaining half of the knuckle member 1 is recessed approximately in the center of the split surface 5a of the upper mold 5. When the upper die 3 is placed on the lower die 5 with the upper and lower split surfaces 5a and 3a in contact with each other, the cavity 7 of the knuckle member 1 is formed. A shell core 8 that forms a hollow hole as the spindle mounting hole 1a is disposed so as to vertically penetrate through the center of the cavity 7, and the shell core 8 has a cylindrical portion 8a that forms the spindle mounting hole 1a, and It consists of a taper 61sab formed above and below the cylindrical part 8a, and a through hole 8c vertically permeable in the center along the entire length of the shell core 8. The upper and lower tapered portions 8b are engaged with the tapered engaging portions of the upper mold 5 and the lower mold 3, respectively. The shell core 8 is manufactured by molding and sintering coated sand. Air introduction holes 9a and 9b communicating with the through hole 8c are formed vertically in the upper mold 5 and the lower mold 3, respectively.
The air outlet 1 communicates with the lower end opening of the air introduction hole 9b.
0 is opened in the center of the surface plate 2. In addition, code 1 in the figure
4 is a sprue, 15 is a runner, and 13 is a hot water reservoir.

The weight 11 is a metal plate for pressing the upper mold 5 against the lower mold 3 from above, and this weight 11 is provided with an opening hole 11a that connects to the sprue 14, and has an opening hole 11a in its interior. An air supply passage 16 connected to the upper end of the air introduction hole 9a of the upper die 5 is transparently provided, and the upstream end of the air supply passage 16 opens at the center of the right side, and the air supply opening 16a
When pressurized air for cooling is supplied from an air supply device (not shown) through a hose, the air flows through the air supply passage 16, the air introduction hole 9a of the upper mold 5, the through hole 8C of the shell core 8, and the lower The air flows through the air introduction hole 9b of the mold 3 and is ejected from the air ejection port 10.

Hereinafter, a casting method for casting the knuckle member 1 from spheroidal graphite cast iron material using the above mold M in the casting stage will be described.

First, as shown in FIG. 3, set the mold M on the surface plate 2, connect the air supply hose of the air supply device to the air supply port 16a, and apply a predetermined pressure (approximately 4.0 kg / Cl1N).
Pressurized air for cooling is supplied to the air supply passage 16 and the upper mold 5.
Air introduction hole 9a, through hole 8C of shell core 8, lower mold 3
The air flows into the air introduction hole 9b and is ejected from the air outlet 10.

While supplying the cooling air, molten spheroidal graphite cast iron is poured from the opening hole 11a and the sprue 14, filling the cavity 7, the sump 13, and the runner 15, and casting.

After the casting is completed, cooling air is continued to be supplied for a predetermined period of time (approximately 90 to 120 seconds) during which the molten metal is solidified and cooled.

As mentioned above, it is not necessarily necessary to supply cooling air before pouring, but it is sufficient to supply cooling air during the process of solidifying after pouring and forming the metallic structure of spheroidal graphite. The molten metal around the spindle mounting hole 1a may be cooled at a cooling rate of about 3.0 to 4.0° C./sec.

After cooling for the predetermined time, the supply of cooling air is stopped, and then the mold M is dismantled under the same predetermined conditions as in the conventional method, and the casting of the Knack JL/NB material 1 is taken out.

As mentioned above, at least during the process of solidifying the molten metal after casting, cooling air is applied to the spindle mounting hole 1 through the shell core 8.
When the area around a is cooled, the cooling rate thereof becomes higher than the cooling rate of other areas, suppressing the coarsening of the spherical graphite particles and making the spherical graphite particles finer.

In this way, since the particles of spherical graphite are made finer, strength and fatigue strength are significantly improved, and workability in cutting and polishing is also improved.

A knuckle member 1 cast by the casting method of the above embodiment,
The experimental results obtained for the knuckle member cast using a solid core without special cooling are shown in Figs. 4 and 5, and in this example, the spindle mounting hole 1a
When the cooling rate in the peripheral area of the graphite was approximately 3.5°C, the particle size of the point graphite was reduced to approximately 25 μm, and in the comparative example, the cooling rate was approximately 25 μm.
．． At 0° C./sec, the particle size of the dotted graphite becomes as large as about 40 μm.

Furthermore, the fatigue strength of the peripheral part of the cast spindle mounting hole la according to the present example is approximately 29.5 kg/mu" (stress amplitude), and the cast spindle device according to the comparative example, hole 1
The fatigue strength of the surrounding area of a is approximately 26.0 kg/ms''.

As is clear from the above experimental data, according to the casting method of the spheroidal graphite iron casting of this example, the spheroidal graphite in the metal structure around the hollow holes of the casting is refined, and its strength, fatigue strength, Cutting performance etc. can be significantly improved.

The knuckle member 1 described above is merely one example, and the casting method of the present invention can be applied to casting methods for casting spheroidal graphite iron castings having various hollow holes. In addition, it is not necessary to use a shell core as the core, and any core with a specified thermal conductivity may be used, and instead of cooling air, other cooling gas, cooling water, or cooling oil may be used. It is also possible to use

[Brief explanation of the drawing]

The drawings relate to embodiments of the present invention; the first drawing is a side view of the knuckle member, the second drawing is a plan view of the lower mold, the third drawing is a cross-sectional view of the mold, and the fourth drawing is a cooling rate and graphite particles. A graph showing the relationship between grain sizes, and FIG. 5 is a diagram showing fatigue strength characteristics. M...Mold, 8...Shell core, 8C...Through hole,
9a, 9b...Air introduction hole, 16...Air supply passage.

Claims (1)

[Claims] (1) In a casting method for casting a spheroidal graphite cast iron casting having a hollow hole, a core having a through hole is used as the core forming the hollow hole, the core is set in a mold, and then formed in the mold. 1. A method for casting spheroidal graphite iron castings, the method comprising: flowing a cooling fluid into a through hole of a core through a passage, at least after pouring the molten metal, to cool the vicinity of a hollow hole of the casting.