JPH0222413A - Production of cast iron parts having remelting chilled layer - Google Patents

Abstract

PURPOSE:To obtain cast iron parts having a remelting chilled layer free from unmelted graphite by forming a layer containing a graphite spheroidizing- inhibiting element on a specific part on the surface of a mold, casting a stock of spheroidal graphite cast iron, and then remelting the specific part of this stock by means of a high-energy beam. CONSTITUTION:A layer 2 containing a spheroidizing-inhibiting element, such as Ti and Ce, is formed on the surface of a mold 1 corresponding to a cam part, etc., requiring wear resistance, of cast iron parts. Then, molten cast iron after spheroidizing treatment is poured into the above mold 1, by which a stock 4, such as camshaft, is cast. Subsequently, the surface (cam part), requiring wear resistance, of the stock 4 is subjected to rough processing to undergo the removal of mill scale (casting surface), and then, the above part is remelted by using a high-energy beam 5 of TIG arc, etc., by which a remelting chilled layer 6 is formed. Since this remelting chilled layer 6 is free from unmelted graphite, the possibility of the occurrence of pitting, etc., is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing cast iron parts having a remelted chill layer.

(Prior Art) Conventionally, when manufacturing cast iron parts that require wear resistance in some parts, such as camshafts in engines, a cold metal is applied to the parts that require wear resistance, such as the cam part, during casting. A method is known in which a chilled layer with excellent wear resistance is obtained by rapidly cooling this portion.

However, recently, as a method for obtaining cast iron parts with higher hardness by increasing the cooling rate faster than the above-mentioned method using a cold metal, and thereby obtaining a cast iron part with higher hardness, the durability of the cast material has been developed. A method has been proposed in which a high-energy beam is used to re-melt a portion where abrasion resistance is required and a chill layer is formed in the re-melted portion.

On the other hand, due to the demand for lighter weight cast iron parts, such as hollow camshafts and thinner shafts, it is advantageous to use spheroidal graphite cast iron, which has excellent mechanical properties and wear resistance, as a material for cast iron parts. It is also known that

Therefore, as exemplified in Japanese Patent Application Laid-Open No. 61-84322, parts of the base material obtained by casting spheroidal graphite cast iron that require wear resistance are remelted using a high-energy beam, and the A method of forming a chill layer in the melted zone has been proposed.

Spheroidal graphite cast iron parts with a remelted chilled layer obtained in this way are advantageous for weight reduction because spheroidal graphite cast iron has higher rigidity than flake graphite cast iron, and also because spheroidal graphite cast iron is added for spheroidization treatment. Since Mg has a deoxidizing effect, it also has the advantage of suppressing blowholes.

(Problem to be Solved by the Invention) However, since spherical graphite has a smaller surface area than flaky graphite, it also has the property of being difficult to melt.

Therefore, when a mold material obtained by casting spheroidal graphite cast iron is remelted using a high-energy beam, graphite may remain in an unmelted state in the remelted chill layer. If graphite remains in an unmelted state as described above, it will cause pitting etc. to occur on the surface of the obtained cast part.

(Object of the Invention) In view of the above, the present invention provides a cast iron part having a remelted chilled layer in which unmelted graphite does not exist in the remelted chilled layer despite using spheroidal graphite cast iron as the material of the cast iron part. The purpose is to provide a manufacturing method.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention is such that the shape of the graphite at the part to be remelted in the mold material of cast iron parts is made into a flaky or caterpillar shape in advance.

Specifically, the solution taken by the present invention is to improve the method for manufacturing cast iron parts having a remelted chilled layer by adding a graphite spheroidization inhibiting element to the surface of the mold corresponding to the part of the cast iron part where wear resistance is required. After that, molten spheroidal graphite cast iron is poured into the mold to cast a material for cast iron parts,
Thereafter, the portions of the mold material corresponding to the portions where wear resistance is required are remelted using a high-energy beam.

(Function) With the above configuration, in the remelting part of the material obtained by casting spheroidal graphite cast iron, the graphite is prevented from becoming spheroidized by the spheroidization inhibiting element, and becomes flaky or caterpillar-shaped. . This flaky or caterpillar-shaped graphite has a large surface area and is easily melted by heat, so when it is remelted by a high-energy beam, it is completely melted.

(Example) Hereinafter, an example of the present invention for manufacturing a cast iron camshaft will be described based on the drawings.

As shown in FIG. 1, spheroidization-inhibiting elements such as Ti, Ce, Ca, and S in the form of powder or slurry are mixed with resin, etc. on the surface of the cam part of a mold 1 consisting of a shell type or metal mold. Layer 2 containing an element that inhibits the spheroidization of graphite
form. The thickness of this layer 2 is 10 μm to 1.5 μm.
It is preferably within the range of 0 mm. The reason for this is that the layer of flaky or caterpillar-shaped graphite formed on the surface of the cam part, which will be described later and is less than 10 μm, is only a rough-processed layer. There is no meaning, 1.
This is because if the thickness exceeds 0 mm, this layer 2 may peel off or the spheroidization-inhibiting element may enter the inside of the mold material to be cast.

Next, as shown in Figure 2, Mg is added to 0.02 to 0.06
A molten cast iron 3 which has been subjected to a spheroidization treatment by adding % by weight is poured into a mold 1 to obtain a camshaft mold material 4 as shown in FIG. The graphite shape in the surface layer of the cam portion of the camshaft material 4 obtained in this way has a depth of 10
It is flake-like or caterpillar-like over a range of μm to 1.0ti11.

Furthermore, the surface of the cam part of this camshaft material 4 is
Rough machining is performed over a range of 0 to 100 μm to obtain a cam portion from which black skin (casting surface) is removed, as shown in FIG.

Next, as shown in FIG. 5, the surface of the cam portion from which the black scale has been removed is remelted using a high energy beam 5 such as a TIG arc, plasma arc, electron beam or laser beam to remelt the chilled layer 6. After forming, the surface of the cam portion is finished to obtain a camshaft 7 as shown in FIG.

When the camshaft 7 is manufactured by the method described above, the graphite in the surface layer of the cam part has a flaky or caterpillar shape, and graphite in this shape has a larger surface area than a spherical one, so it does not absorb heat easily. It has good absorption, and when it is remelted by the high energy beam 5, there is no unmelted graphite in the remelted chill layer 6.

Further, since Mg is added to the molten cast iron for spheroidizing treatment, there are very few blowholes in the remelted chilled layer 6.

In addition, instead of the above example, after adhering a powder alloy sheet for high alloy to the surface of the cam part from which black scale has been removed, this surface is remelted with a TIG arc heat source to obtain a high alloy remelted chilled layer. Even in this case, there is no unmelted graphite in this remelted chilled layer and there are few blowholes.

Hereinafter, specific examples and comparative examples of the present invention, and analysis results in each case will be explained.

Specific Example 1 First, after applying S powder kneaded with vinyl acetate to a thickness of 10 to 30 μm on the surface of the cam part in a shell mold,
This shell type has a weight ratio of C: 3.5% and Si: 2.5%.
A camshaft mold material was obtained by injecting molten cast iron (FCD45) consisting of , Mn: 0.4%, Mg: 0.06%, and the balance Fe.

The inside of this camshaft material had spherical graphite, but only the surface of the cam part had graphite flakes over a depth of approximately 800 μm.

Next, the surface of the cam part of this camshaft material was
After rough machining over a range of 100 μm to remove black scale, the surface of this cam portion was remelted using a TIG arc heat source under irradiation conditions of a beam current of 60A1 and a melting speed of 0°6 m/min.

As a result, the depth of the remelted chilled layer was approximately 1.0 mm, and there were no graphite grains that were residual graphite in this remelted chilled layer, and the blowholes had a diameter of 0.0mm.
There were only 1 to 2 particles of 5a+++ or less generated per IC-, which was very small.

<Specific Example 2> First, Ti powder kneaded with an acrylic resin diluted with a solvent was applied to the surface of the cam portion of a shell mold to a thickness of 10 to 30 μm, and then the shell mold was coated with C:3. 5
%, Si: 2.5%, Mn: 0.4%, Mg: 0.06
A camshaft mold material was obtained by injecting molten cast iron (FCD45) consisting of % Fe and the balance Fe.

The graphite inside this camshaft material was spherical, but only on the surface of the cam portion, the graphite was caterpillar-shaped over a depth range of about 600 to 800 μm.

Next, in the same manner as in Example 1 above, the surface of the cam portion of this camshaft material was rough-processed over a range of 10 to 100 μm to remove black scale, and then the surface of this cam portion was subjected to TIG
Arc heat source, beam current value 60A, melting speed 0.6m/
It was remelted under irradiation conditions for 1 minute.

As a result, the depth of the remelted chilled layer was approximately 1.0+nl11, and no graphite grains remained in this remelted chilled layer, and there were no blowholes with a diameter of 0.5 mm or less. The number was very small, about 1 to 2 pieces per 1 cd.

Specific Example 3 First, in the same manner as in Specific Example 1, S powder kneaded with vinyl acetate is applied to the surface of the cam portion of a shell mold to a thickness of 10 to 30 μm, and then C powder is applied to the shell mold in a weight ratio. :3.5
%, Si: 2.5%, Mn: 0.4%, Mg: 0.06
A camshaft mold material was obtained by injecting molten cast iron (FCD45) consisting of % Fe and the balance Fe.

As in Example 1, the graphite inside this camshaft material was spherical, but only the surface of the cam part had a depth of approximately 800 mm.
The graphite was flaky over the μm range.

Next, the surface of the cam part of this camshaft material was
The black scale was removed by rough processing over a range of 100 μm. Furthermore, C: 2.0%, P: 1.3%, Mo
:5.6% and the balance is Fe, powder particle size is 100
A powder alloy sheet with a thickness of 0.8 mm below the mesh was prepared, and this powder alloy sheet was adhered to the surface of the roughly machined cam part, and dewaxed in H2 gas at a temperature of 300°C for 1 hour. . Thereafter, the surface of the cam portion was subjected to high alloy remelting treatment using a TIG arc heat source to obtain a remelted chill layer.

As a result, the depth of the high alloy remelted chilled layer was approximately 1°0, and its hardness was Hv800. Further, no graphite grains remained in this part, and there were few blowholes.

Comparative Example 1> Shell mold with weight ratio of C: 3.5%, Si: 2.5%, M
When a camshaft material was obtained by injecting molten cast iron (FCD45) consisting of n: 0.4%, Mg 20.06%, and the balance Fe, all parts of this material were made of spheroidal graphite cast iron. Ta.

Next, after rough processing the surface of the cam part of this camshaft material to remove black scale, the surface of this cam part was irradiated with a TIG arc heat source under the irradiation conditions of beam current value 60A1 melting speed 0.6m/min. It was remelted at the bottom.

As a result, the depth of the remelted chilled layer was approximately 1.0 mIm as in Examples 1 and 2, but this remelted chilled layer contained spherical graphite particles with a diameter of approximately 10 to 20 μm in terms of area ratio. 0
．． 4-0.8% remained.

Comparative Example 2> C: 3.4%, 5i11゜4%, M in weight ratio to shell type
When a camshaft material was obtained by injecting molten cast iron (FCHI) consisting of n: 0.6%, Cr: 0.2%, and the balance being Fe, all parts of this material were made of flake graphite cast iron. there were.

Next, after rough processing the surface of the cam part of this camshaft material to remove black scale, the surface of this cam part is irradiated with a TIG arc heat source at a beam current value of 60XA and a melting rate of 0.6 m/min. It was remelted under

As a result, the depth of the remelted chilled layer was approximately 1.5 an, and no graphite particles remained in this remelted layer, but the blowholes were 10I# with a diameter of 10 μm to 1.0 aug. There were 5 to 7 pieces per case.

(Effects of the Invention) As explained above, according to the method for manufacturing cast iron parts having a remelted chilled layer according to the present invention, since the graphite in the remelted part of the ring material has a shape that is easily melted by heat,
When remelted with a high-energy beam, all the graphite is melted. In this way, since no unmelted graphite remains in the parts of the cast iron parts where wear resistance is required, there is no risk of pitting or the like occurring.

[Brief explanation of the drawing]

1 to 6 show the steps of the method for manufacturing cast iron parts having a remelted chilled layer according to the present invention, and FIG. 1 is a cross-sectional view of a layer containing an element that inhibits graphite spheroidization formed in a mold, Figure 2 is a cross-sectional view of the molten cast iron poured into the mold, Figure 3 is a cross-sectional view of the cam part of the camshaft material, Figure 4 is a cross-sectional view of the cam part after black scale has been removed, and Figure 5 is the cam. FIG. 6 is a sectional view of the cam portion of the camshaft. DESCRIPTION OF SYMBOLS 1... Mold, 2... Layer containing a graphite spheroidization inhibiting element, 3... Molten cast iron, 4... Camshaft mold material, 5
...High energy beam, 6...Remelting chill layer, 7
...camshaft.

Claims (1)

[Claims] (1) A layer containing an element that inhibits graphite spheroidization is formed on the surface of a mold corresponding to the part of the cast iron part that requires wear resistance, and then molten spheroidal graphite cast iron is poured into the mold. A cast iron part having a re-melted chilled layer is characterized in that a material for the cast iron part is cast using a high-energy beam, and then the part of the material corresponding to the part where wear resistance is required is remelted using a high-energy beam. Production method.