JPS60255256A - Casting method - Google Patents

Abstract

PURPOSE:To form a corrosion- or wear-resistant alloy layer on the surface layer part of a casting by setting a magnetized chiller in a casting mold, sticking magnetically a ferrous powder alloy to the chiller and melting said powder alloy by the heat of the molten metal cast into the casting mold. CONSTITUTION:The magnetized iron or steel chiller 5 is set to the prescribed point in the cavity 4 of a sand mold 3 and the ferrous powder alloy 6 having the characteristic such as corrosion resistance, wear resistance or lubricity is magnetically stuck on the surface of the chiller 5. The molten metal is then cast into the cavity 4 and the alloy 6 stuck magnetically to the chiller 5 is melted by the heat of the molten metal to form the alloy layer having the desired characteristic to the surface layer part of the casting. The casting may be ferrous or nonferrous as far as the powder alloy can be magnetically stuck to the chiller. The alloy layer having the desired characteristic is thus formed only to the optional part of the casting.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a casting method for forming an alloy layer with excellent corrosion resistance, wear resistance, etc. on the surface of a cast product.

[Technical background of the invention]

Some cast products have sliding surfaces or fitting parts with other parts, and these sliding surfaces or fitting parts have better corrosion resistance and wear resistance than other parts. high standards are required.

For this reason, methods for casting gods have been proposed for a long time.

For example, when performing centrifugal casting, a metal or alloy with properties such as wear resistance and high density is mixed into the molten metal, and the centrifugal force concentrates the metal or alloy on the outer surface of the cast product. A method of coating the surface of the core used during casting with metal or alloy powder having properties such as wear resistance, and a method of applying metal or alloy powder having properties such as wear resistance to the molten metal, such as Ni,
Or.

There are many methods such as directly adding Ti, Mo, etc., setting a cooling metal in a part of the mold, and rapidly cooling the molten metal in contact with this cooling metal to form a highly hard chilled layer. be.

[Problems with background technology]

However, when centrifugal casting is performed by adding a metal or alloy with specific properties to the molten metal, it is possible to form an alloy layer with excellent wear resistance only on the outer surface of the cast product. For example, it is impossible to form an alloy layer with excellent wear resistance on the inner periphery of a through hole of a cast product in which a through hole for fitting is formed.

In addition, in the method of applying metal or alloy powder to the surface of the core, a binder is necessary for application, and the heat during casting fuses (reacts) the binder and the metal powder or molten metal into a composite kasuri. ), producing harmful gases and inclusions, which can cause manufacturing defects.

The method of directly adding Ni, Or, Ti, Mo, etc. to the shredded molten metal requires a large amount of expensive metal, and it is difficult to impart the above effects to parts where properties such as wear resistance are not required. In fact, it makes cutting, etc., more difficult.

Furthermore, in the method of using a chilled metal, the surface of the cast product is rapidly cooled, so cementite precipitates and the hardness becomes too high, making it easy to become cracked ferrite, which deteriorates the wear resistance. However, corrosion resistance will not improve.

[Purpose of the invention]

The present invention was developed in view of the problems of the conventional casting method described above, and its purpose is to improve the quality of parts that require properties such as corrosion resistance or abrasion resistance, such as sliding surfaces and fitting parts of cast products. The object of the present invention is to provide a casting method that can easily form an alloy layer having excellent properties.

[Summary of the invention]

In order to achieve the above object, the present invention sets a magnetized cold metal in a V) mold, magnetically attaches an iron-based powder alloy to the cold metal in advance, and then pours the molten metal into the mold. By casting,
The heat of the molten metal melts the iron-based powder alloy, which has been magnetically attached to the cold metal, to a melting rate of 1.
The outline is that the entire alloy layer is formed with excellent properties such as anti-wear properties.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a sectional view of a mold used to carry out the method of the present invention, and specifically, a sectional view of a mold used for casting a rotating plate for a thrust bearing of a rotating electric machine.

That is, the mold 1 is formed by forming a sand mold 3f in the casting flask 2, and a magnetized steel chiller 5f is set in a predetermined position in the cavity 4 of the sand mold 3. The shape of this cooling metal 5 is made to follow the surface shape of the intended cast product. Therefore, when forming an alloy layer with specific properties only on a part of the surface of a cast product, the chiller 5 is set in the part corresponding to the part, and when forming an alloy layer on the entire surface. Set the chilled metal 5 over the entire surface of the cavity.

Next, iron-based alloy powder 6 having desired properties such as corrosion resistance, wear resistance, or lubricity is magnetically attached to the surface of the set cold metal 5. The alloying element constituting this iron-based alloy powder may be any metal that fuses with iron, and the ratio of iron to the alloying element must be within a range that does not lose magnetization ability, that is, a ratio that can be magnetically attached to the cold metal 5. good. The particle size of the alloy powder is selected depending on the thickness of the intended cast product, but is preferably 1 m or less.

With the iron-based alloy powder 6 magnetically attached to the cold metal 5 in this manner, the cavity 4 is filled with molten metal.

Then, the alloy powder 6 is melted by the heat of the molten metal, and an alloy layer having excellent corrosion resistance, wear resistance, and lubricity is formed on the surface of the cooled bale material. Further, the boundary between the alloy layer and the base material fuses with each other.

Next, a specific experimental example will be described. The thrust bearing of a rotating electric machine was a rotary plate for the cast member, and an alloy layer with excellent wear resistance and lubricity was formed on the thrust surface of the rotary plate. The alloy powder used to form the alloy layer was Fθ
-0u-Ti alloy (Ou: 1% or more, Ti: 0.5% or more, Fθ: balance). Here, C'u is an element that promotes gradual graphitization and refines the pearlite in the base, and T'i is a strong element that promotes graphitization and has casting metallurgical properties that produce eutectic graphite. It is preferable as a metal element constituting the wood powder in the invention method. In addition, the molten base metal to be cast into the mold had a component corresponding to JIS Fe12 material, and was cast at 1420C.

The metal structure of the alloy layer of the rotating plate obtained as described above is shown in reference drawings (a) to ) as micrographs.

The reference drawing (a) shows the metal structure of alloy l- from the surface 5 to 7 degrees, with two phases of fine pearlite and ferrite forming the base, and graphite showing a clear eutectic shape and its shape being AS.
It exhibits a TMOE type. Also reference drawings (b) and (c)
, 2) are respectively 10 + m + 1.15 meters from the surface.

The metal structure at a depth of 30W+ is shown, and the matrix (base) in both cases consists of pearlite and ferrite.
At a distance of 10 mm from the surface, the graphite shape exhibits the D shape of AsTM, and at a distance of 15 mm, it exhibits a fine shape, 30wn.
The part shown here is fully grown type A.

Cementite precipitation is not observed in any of the structures. If cementite is precipitated, a chilling phenomenon will occur as mentioned above, which will significantly harden the thrust surface, making machining difficult and causing abrasion of the mating member. It can be seen that when the alloy powder containing 'ii is used, there is no precipitation of cementite and excellent properties are exhibited.

On the other hand, Figure 2 is a graph showing the relationship between the depth from the surface of the alloy layer and the hardness in the above experimental example.As is clear from this graph, the layer from the surface to 80 mm has sufficient hardness. It can be seen that the hardness gradually decreases toward the inside, and when it reaches 15 mm or more, it maintains a hardness equivalent to that of FC20 material and remains constant.

The above is an example of implementation. For example, in the case of cast steel castings, if elements with corrosion resistance such as Or and Ni are used as alloy powder, an alloy with excellent corrosion resistance can be formed only in the necessary surface layer. A layer can be formed, and the shape of the alloy powder may be arbitrary, such as granular. For example, the surface of iron particles may be coated with an alloying element. In short, any material that can be magnetically attached to the magnetized cold metal may be used. If such a coated product is used, it can also be applied to steel castings, Ou castings, etc.

〔Effect of the invention〕

As explained above, according to the present invention, the cold metal set in the mold is magnetized, and the molten metal is filled with the iron-based alloy powder magnetically attached to the cold metal. It is possible to easily form an alloy layer having desired characteristics on any part of a casting, regardless of whether it is ferrous or non-ferrous.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a mold used in carrying out the method of the present invention, and FIG. 2 is a graph showing the relationship between the depth of the alloy layer and the hardness. l... Mold, 3... Sand mold, 4... Cavity, 5
... Chilled gold, 6... Iron-based alloy powder. Applicant's agent Kiyoshi Inomata (aX

Claims (1)

[Claims] A magnetized cold metal is set in a mold, an iron-based powder base metal is magnetically attached to the cold metal, and then molten metal is poured into the mold, and the iron-based powder alloy is melted by the heat of the molten metal, and then cast. A casting method characterized by forming an alloy layer having characteristics such as corrosion resistance and wear resistance on a part of the product.