JPH02274886A - Production of high-alloy remolten cam - Google Patents

Abstract

PURPOSE:To well convert a cam surface to a high alloy without generating quenching cracks by adhering an alloy powder sheet to the prescribed range of the surface of a cam base material, then irradiating the base material with a high energy beam by starting the irradiation from the exposed part of the material, and thereby remelting the material. CONSTITUTION:A binder resin is mixed with alloy powder contg. carbide forming elements in form the sheet of the alloy power. This alloy powder sheet 4 is adhered to the prescribed range on the surface of the base material 3 of the cam 2 disposed on a cam shaft 1. After the alloy powder sheet 4 is degreased, the alloy powder sheet 4 and the surface of the base material 3 are remelted by the high energy beam generated by the TIG arc from a TIG torch 5 having an electrode 6 to form the high alloy layer. The abovementioned remelting is started from the exposed part on this side where approximately the entire width of the surface of the base material 3 is coated with the abovementioned sheet 4. The base material 3 is sufficiently preheated in this way to prevent the rapid cooling of the remolten layer and to prevent the generation of the quenching cracks at the point near the remelting start point, by which the high alloying of the cam 2 surface is well performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a high alloy remelting cam used as a valve driving cam of an engine.

[Prior Art] The valve drive cam of an engine, which rotates in sliding contact with a rocker arm, tappet, etc., is required to have high wear resistance.

In order to increase the wear resistance of this cam, it is known to remelt and harden the cam surface with a high energy density heat source. In other words, when the surface of a cast iron cam is remelted using a heat source with high energy density, it is rapidly cooled by heat conduction to the inside, forming a fine and highly hard chilled layer. By supplying carbide-forming elements, it is possible to obtain a high-alloy remelted layer with high hardness different from the composition of the base material.

Conventionally, as a surface hardening treatment for metal members such as cams that require such wear resistance, for example, Japanese Patent Application Laid-Open No. 60-23098
As shown in Publication No. 6, an alloy powder sheet layer is formed on the surface of a metal member by, for example, bonding a sheet made by mixing binder resin with alloy powder to a base material, and after dewaxing treatment is performed. , laser beam, electron beam, TIG arc (TIG arc - tungsten inert gas arc)
A method is known in which the alloy powder sheet layer and the surface of the base material are simultaneously remelted by irradiation with a high-energy beam such as the above, thereby achieving high alloying.

(Problem to be Solved by the Invention) When manufacturing a high-alloy remelted cam using the above-described method, when remelting with a high-energy beam, there is a problem in which the alloy powder sheet layer is formed. There was a problem in that quench cracks were likely to occur near the remelting start point.

That is, the portion where the alloy powder sheet layer is formed increases in hardness due to remelting, which increases carbides and improves hardenability, but on the other hand, if the cooling rate is fast, quench cracking occurs. After forming an alloy powder sheet layer on a predetermined range of the surface of the base material of the cam installed on the camshaft, when remelting this area, the camshaft is rotated at a constant speed while the alloy powder sheet layer is melted. A high-energy beam is irradiated from one end of the forming part, but since the cam temperature is low at the beginning of this remelting, the cooling rate of the part near the remelting start point is faster than other parts. Therefore, quench cracking is likely to occur in the portion on the side of this remelting start point.

As a countermeasure to this problem, it is conceivable to preheat the camshaft during remelting to slow down the cooling rate of the portion closer to the remelting start point.

However, since the camshaft has a large number of cams and these are remelted one after another, preheating the entire camshaft until the last cam is remelted will require a long preheating time, and the alloy powder will It has a large surface area and is easily oxidized. For this reason, if the preheating temperature is increased to about 350° C. or higher, the alloy powder sheet will abnormally oxidize during preheating and fall off from the base material.

On the other hand, if the preheating temperature is lowered to about 350° C. or lower, the effect of slowing down the cooling rate of the portion on the side of the remelting start point becomes insufficient, and the occurrence of quench cracking cannot be prevented. Therefore, by simply preheating the camshaft, it is not possible to prevent both the occurrence of quench cracking and the oxidation and falling off of the alloy powder sheet.

In view of these circumstances, the present invention prevents the alloy powder sheet from being abnormally oxidized and falling off from the base material, and at the same time prevents the occurrence of quench cracking in the part on the side of the remelting start point. The object of the present invention is to provide a method for manufacturing a high-alloy remelted cam, which can prevent the above-mentioned problems and satisfactorily make the cam surface highly alloyed by remelting.

[Means to solve the problem]

In order to achieve the above objects, the present invention adheres an alloy powder sheet, which is a mixture of alloy powder and binder resin, to a predetermined area of the surface of the cam base material, and then irradiates it with a high energy beam. A method for manufacturing a high-alloy remelting cam in which a high-alloy layer is formed by remelting an alloy powder sheet and the surface of a base material, the method comprising: remelting with the high-energy beam; It starts from the exposed part of the base material, which is closer to the covered part.

[Effect]

According to the above configuration, when the exposed part of the base material is irradiated with a high-energy beam, the heat transmitted from this part sufficiently raises the temperature of the starting end of the part where the alloy powder sheet is bonded, and when it is remelted. Rapid cooling of this part is suppressed. In addition, abnormal oxidation of the alloy powder sheet is prevented by using a high-energy beam for remelting to raise the temperature in a short time immediately before the bonded portion of the alloy powder sheet is remelted.

〔Example〕

Examples of the method of the present invention and comparative examples will be described with reference to the drawings.

First Example> First, an alloy powder containing a carbide-forming element and 7, an acrylic resin as a binder resin are mixed to form an alloy powder sheet. As a specific example, MO: 2.
5 to 15.0 wt%, Cr: 10 wt% or less, P: 0.
5 to 3.0 wt%, C: 1.5 to 5.0 wt%, Fe:
A eutectic alloy powder containing the remainder of An alloy powder sheet was formed.

To explain the above components, MO combines with Fe and C and contributes to strengthening the base and forming a hard phase,
It plays the role of lowering the melting point. This 1ylo is 2
．． If it is less than 5 wt%, the hard phase will decrease, the amount of liquid phase will decrease, making it difficult to alloy, and
If it exceeds 2.5 to 15.0 wt%, the amount of liquid phase will be too large, resulting in brittleness and a significant decrease in toughness.
Good range. Cr contributes to improving wear resistance and hardenability due to its carbide. This C
If r exceeds 10 W%, it will be saturated, so Cr is preferably 10 wt% or less. P is F8. It combines with carbon to improve wear resistance and lower the melting point. If this P is less than 0.5 wt%, the amount of liquid phase will be small and will not contribute to alloying, and if it exceeds 3.0 wt%, there will be too much liquid phase and it will be difficult to secure the shape, so P is 0. A range of .5 to 3.0 wt% is preferable. C strengthens the matrix, forms a hard phase, and is useful for alloying. If this C is less than 1.5 wt%, lowering the melting point will be inhibited, and if it exceeds 5.0 wt%, the amount of liquid phase will be too large and it will be difficult to maintain the shape.
The Qwt% range is good.

Next, as shown in FIGS. 1 and 2, the above alloy powder seeds '4 are applied to a predetermined area of the surface of the base material 3 of the cam 2 disposed on the camshaft 1 using an acrylic adhesive tape. Glued. As shown in Fig. 2, the area to which the alloy powder sheet 4 is bonded is the area from 13 degrees before the cam lift part to the symmetrical position on the opposite side through the cam nose part, and in this range, the alloy powder is applied to approximately the entire width of the cam base material 3. Sheet 4 was adhered.

Incidentally, the surface of the cam base material 3 had black scale removed after casting, and the surface roughness was set to 4S or less.

After dewaxing the camshaft 1 with the alloy powder sheet 4 adhered to the cam surface by holding it in N2 gas at a concentration of 3000 for 1 hour, as shown in FIG. The remelting process was performed using a high-energy beam. This remelting process is performed by oscillating the TIG torch 5 in the width direction of the cam while rotating the camshaft 1 at a constant rotational speed with the electrode 6 of the TIG torch 5 brought close to the cam surface in an inert gas. By moving the alloy powder sheet 4), the arc generated between the electrode 6 and the cam surface sequentially remelts the cam surface to which the alloy powder sheet 4 is adhered. In particular, as shown in FIG. 4, this remelting is started from the exposed part of the base material on the front side of the part where the alloy powder sheet 4 is bonded,
In other words, a predetermined range on this side of the highly alloyed remelting zone A where the alloy powder sheet 4 is remelted together with the base material surface,
A pre-base material mm zone B where only the base metal 3 is remelted was set, and remelting was performed using a TIG arc from this base metal remelting zone B to the highly alloyed remelting zone A.

The TIG treatment conditions during this remelting are shown in Table 1.

Table 1. TIG processing conditions Under these conditions, if the base material remelting zone B is set at 77° or more, that is, remelting is started at 77° or more before the end of the remelting start side of the highly alloyed remelting zone A. ,
The remelting start side end of the highly alloyed remelting zone A is 400~
Since the temperature was raised to 500°C and the cooling rate was reduced, no cracks (quenching cracks) occurred.The range of base material remelting zone B necessary to prevent cracks from occurring is as follows:
If the conditions such as melting speed are changed, it will change accordingly, and when manufacturing Karasu alloy remelting cams, based on the setting of remelting processing conditions, etc., the base material remelting zone should be experimentally investigated in advance. All you have to do is set the range of B.

<Comparative Example 1> The molding of the alloy powder sheet 4, the adhesion to the cam surface, and the remelting treatment conditions as shown in Table 1 were the same as in the first example, and the range of the base material remelting zone B was set to 76 If remelting is performed with the setting below °, highly alloyed remelt zone A
Because the temperature at the end of the remelting start side was insufficient, cracks occurred in this part.

Comparative Example 2> When the entire camshaft was preheated to over 400'C, the alloy powder sheet adhered to the cam surface was abnormally oxidized and fell off from the base material during preheating, making it impossible to remelt it. .

<Second Example> Instead of providing the base material remelting zone as in the first example,
As shown in FIG. 5(a) or FIG. 5(b), by forming the ends of the alloy powder sheet 4 in a shape such as a corner or an arc shape, substantially the entire width of the base material surface is In front of the highly alloyed remelting zone A, which is covered with Remelting was carried out from zone C. Even in this case, quench cracking can be avoided by lowering the high alloying ratio in zone C, and while remelting of zone C is being carried out, remelting to the highly alloyed remelting zone starts. Since the temperature of the side portions was sufficiently raised, it was effective in preventing quench cracking. In this second embodiment, remelting may be started further before zone C.

〔Effect of the invention〕

As described above, in the present invention, when an alloy powder sheet is bonded to a predetermined area on the surface of a cam base material and then remelted by irradiation with a high-energy beam, substantially the entire width of the base material surface is covered with the alloy powder sheet. Since remelting is started from the exposed part of the base material on this side of the covered part, by irradiating the exposed part of the base material with the high-energy beam,
The temperature of the remelting start side end of the portion covered with the alloy powder sheet can be sufficiently raised in the dark for a short time. Therefore, it is possible to prevent the alloy powder sheet from falling off due to abnormal oxidation, and to prevent quench cracking due to rapid cooling of the portion to be highly alloyed.

[Brief explanation of drawings]

1 and 2 are a schematic side view and a schematic front view showing the step of adhering the alloy powder sheet to the surface of the cam base material in the first embodiment of the method of the present invention, and FIG. 3 is a schematic perspective view showing the remelting process. 4 are schematic front views showing the range of remelting, and FIGS. 5(a) and 5(b) are schematic side views showing the second embodiment, respectively. DESCRIPTION OF SYMBOLS 1... Camshaft, 2... Cam, 3... Cam base material, 4... Alloy powder sheet, 5... Tig torch,
6...electrode. Patent applicant Mazda Co., Ltd. Agent
People Patent Attorney Etsushi Kotani
Chief Patent Attorney 1) Patent Attorney 1
Takao Ito (b)

Claims (1)

[Claims] 1. After adhering an alloy powder sheet, which is a mixture of alloy powder and binder resin, to a predetermined area on the surface of the cam base material, the alloy powder sheet and the base material surface are remelted by irradiation with a high-energy beam to increase the A method for manufacturing a high-alloy remelting cam forming an alloy layer, wherein the remelting using the high-energy beam is performed by exposing the base material on the front side of the part where substantially the entire width of the base material surface is covered with the alloy powder sheet. A method of manufacturing a high-alloy remelting cam, the method comprising starting from a section.