JPS58112651A - Casting method for chilled cam shaft - Google Patents

Abstract

PURPOSE:To prevent the generation of misrun and to form good chill layers, by charging molten cast iron into the cavity disposed with chillers in required positions, and sucking the air in the cavity through the wall surface of a mold. CONSTITUTION:A shell mold 3 having a cavity 2 conforming to a cam shaft is held with backup materials 4, and is contained in a vessel 5, whereby a mold 1 is constituted. Chillers 6 are embedded in the wall surfaces facing the cam noses in the many projecting parts corresponding to the cams in the cavity 2. The bottom surface of the vessel 5 has many vent holes 7, and the vessel 5 is placed on a suction box 8 in such a way that the opened part on the top surface of the box 8 is closed with said bottom surface. While the air in the box 8 is sucked with a pump, molten cast iron is charged into the cavity through a sprue 10. Then negative pressure is developed in the cavity 2, and the molten metal flows over the entire part of the cavity 2, whereby the generation of misrun is effectively prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for casting a chilled camshaft, and more particularly, to a method for casting a sound chilled camshaft having a good chill layer at necessary locations. A chilled camshaft casting method is known in which a chilled layer is formed on the surface of a cast iron part at a predetermined location by casting the camshaft using a chilled mold coated with gold. The mold cavity is long and has a complex shape with many cavity protrusions corresponding to the cams, and a cold metal is placed at each end of the protrusions, making it difficult to pour into the mold. The molten cast iron is cooled by a large number of chillers within the cavity, and as a result, defects due to poor circulation tend to occur frequently. In order to prevent this poor flow, it is effective to raise the pouring temperature, but if the pouring temperature is too high, the casting surface of the casting will deteriorate.
This will occur if the number of post-processing steps increases. However, when a large chiller is used to form a chill layer of a predetermined thickness, there are problems such as difficulty in holding the chiller in the casting 11.

On the other hand, it is effective to lower the pouring temperature in order to form a smooth chill layer, but lowering the pouring temperature tends to cause the aforementioned poor circulation; There is a limit to how much you can lower it.

In view of the above-mentioned circumstances, an object of the present invention is to provide a casting method that forms a good chilled layer at a predetermined location, prevents poor hot water circulation, and makes it possible to cast a sound chilled camshaft. It was created using a mold with cooling metals placed at predetermined locations on the inner wall of the cavity.
The present invention relates to a method for casting a chilled camshaft in which molten cast iron is injected into the cavity, characterized in that air in the cavity is sucked through a wall surface of the mold when the molten cast iron is injected.

Next, the method of the present invention will be explained with reference to the accompanying drawings.

In FIG. 1, which shows casting of a chilled camshaft, a shell mold 3 having a long cavity 2 corresponding to the camshaft is housed in a container 5 together with a back-up material 4 for fixing the shell mold to constitute a casting fjIi1. are doing. The cavity 2 of the shell casting 113 is located at a predetermined location,
That is, a cooling metal 6 is embedded between the walls corresponding to the cam noses of a large number of cavity protrusions corresponding to the cams, and the surface of the wrinkled cooling metal constitutes a part of the inner wall of the cavity 2. ing.

The container 5 has a plurality of ventilation holes 7 on its bottom surface, and is placed on the suction box 8 so that the bottom surface of the skeleton container 5 closes the top opening of the suction box 8. The suction box 8At has a flow hole in its side wall, and communicates with an exhaust pump (not shown) through a ventilation cylinder 9.

Note that it is desirable to place a shield 11 on the upper surface of the mold, covering most of the mold except for the sprue 10.

After assembling the mold as described above, remove the exhaust pump (not shown).
When activated, the air in the suction box 8 is sucked by the pump, and at the same time, the air in the mold cavity 2 is sucked through the casting hole wall surface and through the vent hole 7.

When molten cast iron is injected from the sprue 10 in the above condition, the air in the cavity is sucked through the mold wall 'rMt-, and is guided by the air flow generated in the cavity, and the air pressure in the wrinkled cavity is reduced. Due to the negative pressure compared to the outside pressure, the molten cast iron quickly flows to every corner of the cavity, effectively preventing defects caused by poor metal circulation even though it is cooled by a chiller. Ru.

Therefore, according to the method of the present invention, it is possible to pour at a lower temperature than the pouring temperature for chilled cast iron that has been generally adopted in the past, and it is possible to improve the cooling effect of the chilled metal by pouring at a lower temperature. This makes it possible to form a smooth chill layer.

Regarding the pouring temperature adopted in the method of the present invention, C3
, O~4.0%, 8i 1.2~3.0%, CrO,
General chilled cast iron containing 1 to 2% Mn, 1.5% or less of Mn, the balance being substantially KFe, and further containing 2 to 4% Ni, MOo, 25% U (0.5%) as necessary. te1
A chilled molder with a good chill layer and no casting defects at a low temperature in the range of 180 to 1370°C. It will be easily understood that the same phenomenon will occur even if suction is started at the same time as the injection of molten cast iron or immediately after the injection starts, and therefore the same effect can be obtained.

[Experimental Example 1] A shell mold for a camshaft with a shaft diameter of 24 mm, a total length of 600 cm, and 12 cams on the shaft with a width of 15 mm and a nose height of 22 N1 at intervals of 595 m was manufactured.

Here, on the inner wall of the cavity corresponding to the cam north part, a cast iron 1-piece chiller weighing 60 fr was disposed at a position facing the tray having the same width as the cam width and covering about half of the outer peripheral surface of the cam. The above-mentioned shell mold was backed up with sand in a container with a ventilation hole on the bottom, and the container was placed on a suction box, and while being suctioned and evacuated with an exhaust pump, C3.5%, Si1.9 %, Mn0.2%, Po, 0
A molten cast iron having a chemical composition of 6% Cr, 0.12% Cr, and the balance substantially Fe was poured at 1400° C. to obtain a casting material for a camshaft.

No defects attributable to poor molten metal circulation were observed in the obtained camshaft casting material.

In addition, the surface roughness of the casting surface of the casting material is 10089 degrees,
The chill layer formed on the cam nose part of the cam near the sprue tended to have a slightly thinner chill depth, and the chill depth of the cam as a whole varied. A chill layer was formed. A sketch of the obtained chill layer of the cam nose portion is shown in FIG. The chill layer has a two-layer structure consisting of an outermost completely chilled layer 12 and a coexistence layer 13 of carbide and graphite below it, and the thickness a of the complete chill layer and the thickness b of the coexistence layer are respectively 3. It was 5■, 4 deception.

[Experimental Example 2] (Comparative Test) Using a mold with the same configuration as that used in Experimental Example 1, but without operating the exhaust pump, molten cast iron with the same composition as above was heated at the same temperature as in Experimental Example 1. Molten metal was poured to obtain a casting material for a camshaft.

The resulting casting material for a camshaft had numerous defects at its tip, particularly near the cam nose, due to poor molten metal circulation, and could not be used as a product.

[Experiment Example 3] Using a mold with the same configuration as that used in Experiment Example 1, molten cast iron having the same composition as in Experiment Example 1 was poured at a lower temperature to 125
Molten metal was poured at 0°C to obtain a casting material for a camshaft.

The obtained casting material for a camshaft had no defects at all due to poor molten metal circulation, and the casting surface had a good surface roughness of about 188. Further, as shown in Fig. 3, the thickness a of the complete chill layer 14 is 10 mm, the thickness b of the coexistence layer 15 is 4.5 mm, and the chill layer of each cam nose portion is approximately It was well formed at the same depth.

[Experimental Example 4] (Comparative Test) Using a mold with the same configuration as that used in Experimental Example 1, but without operating the exhaust pump, molten cast iron with the same composition as above was poured at the same pouring temperature (1250°C) as in Experimental Example 3. ℃) to obtain a casting material for a camshaft.

The obtained camshaft casting material had many defects at its tip due to poor molten metal circulation, and was in a state unsuitable for use as a product.

As mentioned above, in the method of the present invention for casting a chilled camshaft, the air inside the cavity is sucked through the wall surface of the cavity during the pouring process, so the molten metal flows quickly inside the cavity and is therefore cooled. Even though it is cooled by gold, it is possible to cast a sound chilled camshaft without poor hot water circulation, and since hot water circulation is good in the cavity, low temperature pouring allows for good casting. Its industrial value is extremely great as it enables the formation of chilled layers.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating an example of a mold configuration used in carrying out the method of the present invention, and FIGS. 2 and 3 are sectional views illustrating a chill layer of a cam nose portion.

Claims (1)

[Scope of Claims] 1) A method for casting a chilled camshaft in which molten cast iron is injected into the cavity using a mold in which chilled metal is placed at a predetermined location on the inner wall of the cavity, according to -b, the molten cast iron is injected. A chilled camshaft casting method characterized in that the air in the cavity is sometimes sucked through the mold wall surface 2) Contains 0 to 40% C, 1.2 to 3.0% Si, and the balance alloying elements and accompanying elements. 2. The method for casting a chilled camshaft according to claim 1, wherein the cast iron is poured into a molten cast iron substantially consisting of Fe at a temperature within the range of 1180 to 1370°C.