JPH036319A - Method and device for remelting and hardening of cast iron casting - Google Patents

Abstract

PURPOSE:To allow the perfect remelting and hardening treatment by pressing a cooling means to the part which is to be treated and is small in volume and low in self-cooling effect at the time of subjecting the part to be treated of the cast iron casting to the remelting and hardening treatment. CONSTITUTION:A square chip-shaped pad part 2 as the part to be treated is integrally formed to the front of the cast iron casting, for example, a rocker arm 1. The rear of the pad part 2 is reinforced to a T shape in section in a rib part 3 which is likewise integrally formed. The pad part 2 is, therefore, small in volume and is low in the self-cooling effect. A pressurizing means 7 is actuated to bring the cooling means 6 into tight contact with the side face of the pad part 2 before, during or right after the heating at the time of heating and remelting at least the surface part of the pad part 2 by a melting means 5, such as TIG torch by using the device for remelting and hardening treatment 4. The cooling means 6 is exemplified by a chill mold of a water cooled or air cooled structure consisting of copper, etc., which can be made into tight contact with the pad part 2. The pad part 2 is force-cooled by this method, by which the cooling rate is increased and the perfect chilling is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a remelting hardening treatment method carried out to improve the wear resistance of various cast iron castings, and an apparatus used in the method.

[Prior Art] When there is a part of a cast iron casting whose wear resistance is desired to be improved (referred to as a treated part in this specification), it is easy and convenient to chill the treated part by remelting and hardening treatment. Effective.

As shown in FIGS. 4 and 5, a conventional method of remelting and hardening a pad portion 2 as a treated portion, taking as an example a rocker arm 1 as a cast iron used in a valve mechanism of an internal combustion engine. To explain, the pad portion 2 is
G (tungsten inert gas) After being locally heated and remelted by a melting means 5 such as a torch, the pad portion 2 is
The hardness is increased by self-cooling and chilling.

[Problems to be Solved by the Invention] However, like the pad portion 2 of the rocker arm 1,
If the volume of the treated part is small and the self-cooling effect is low, the cooling rate during the self-cooling process will be slow, leading to graphite precipitation and coarsening of the chilled structure, resulting in insufficient hardness and less than expected durability. There was a problem that abrasion resistance could not be obtained. 6th
The figure is a photograph (magnification: 400x) of the structure of the pad portion 2 after remelting and hardening treatment according to the conventional method, and it can be seen that precipitation of graphite and coarsening of the chilled structure have occurred.

In order to prevent this problem, it is necessary to increase the volume of the treated part of cast iron castings to increase the self-cooling effect, but increasing the volume of the treated part is difficult or difficult due to performance and design issues. It may not be possible. For example, in the case of the rocker arm 1, if the volume of the pad portion 2 is increased,
This is not preferable because the inertial mass of the rocker arm 1 increases and the ability to follow high-speed operation of the internal combustion engine decreases.

It is an object of the present invention to solve the above-mentioned problems and provide a method and apparatus that can completely remelt and harden even a treated part having a small volume and low self-cooling effect. .

[Means for Solving the Problems] In order to achieve the above object, in the remelting hardening treatment method according to claim 1, the treated portion of the cast iron casting is heated and remelted, and the treated portion is self-cooled. In the remelting and hardening treatment method of cooling and chilling, a cooling means is pressed against a part to be treated which has a small volume and low self-cooling effect before, during or immediately after heating, and the part to be treated is forcibly cooled. I took this method.

The remelting and hardening treatment apparatus according to claim 2 further includes a melting means for heating and remelting a portion to be treated of a cast iron casting, a cooling means that can be brought into close contact with the portion to be treated, and a cooling device that connects the cooling means to the portion to be treated. and a pressing means for removably pressing against the holder.

[Effect] Even if the treated part has a small volume and low self-cooling effect,
By pressing the cooling means against the processing target part before, during or immediately after the heating, forced cooling by the cooling means is performed in addition to self-cooling of the processing target part, thereby increasing the cooling rate. Therefore, complete chilling occurs, and precipitation of graphite and coarsening of the chilled structure as in the conventional example are suppressed.

[Example] Hereinafter, a first example will be described in which the present invention is embodied in a method and apparatus for remelting and hardening the pad portion of a rocker arm.
This will be explained with reference to FIGS.

A square chip-shaped pad part 2 as a treated part is integrally molded from cast iron at the tip of the rocker arm 1 which is a cast iron casting, and the back surface of the pad part 2 has a T-shaped cross section with a rib part 3 which is also integrally molded. Reinforced. Therefore, this pad portion 2 has a small volume and a low self-cooling effect.

The remelting and hardening processing apparatus 4 of this embodiment includes a melting means 5 that heats and remelts at least the surface portion of the pad portion 2;
It is composed of a cooling means 6 that can be brought into close contact with the side surface of the pad section 2, and a pressing means 7 that presses the cooling means 6 against the side surface of the pad section 2 in a detachable manner.

The melting means 5 is not limited to a specific one as long as it is capable of local heating, and examples thereof include a known TIG torch, plasma torch, electron beam device, laser device, and the like. A TIG torch is not used in this example.

The cooling means 6 is not limited to a specific one as long as it has good thermal conductivity and heat resistance and substantially matches the side shape of the pad section 2, and may have a water-cooled structure or an air-cooled structure made of copper, aluminum, etc. An example is a chilled metal. In this embodiment, two chillers are used, which have a water cooling structure by providing a water channel 6a in a copper block having the same shape as the side surfaces of the pad part 2 and the rib part 3. Make sure it touches both sides.

The pressing means 7 is not limited to a specific one as long as it is capable of reciprocating motion, and may be a pneumatic cylinder, a hydraulic cylinder,
Examples include electromagnetic solenoids and combinations of these with link mechanisms.

In this embodiment, two pneumatic cylinders were used which horizontally drive two chillers serving as the cooling means 6 so as to face each other.

Now, the remelting hardening treatment method of this embodiment is carried out using the above-mentioned remelting hardening treatment apparatus 4, and as shown in FIGS. 1 and 2, at least the surface portion of the pad portion 2 of the rocker arm 1 is When remelting by heating with the melting means 5, the cooling means 6 is pressed against the side surface of the pad portion 2 by operating the pressing means 7 before, during or immediately after heating, and the cooling means 6 is pressed against the side surface of the pad portion 2. The purpose is to forcibly cool the pad section 2.

By adopting the above method, even if the pad portion 2 has a small volume and a low self-cooling effect, forced cooling by the cooling means 6 is performed in addition to the self-cooling, so that the cooling rate becomes faster. Therefore, complete chilling occurs and the precipitation of graphite and coarsening of the chilled structure as in the conventional example are suppressed, so that the hardness is sufficiently increased and the expected wear resistance can be obtained. Figure 3 shows
A photograph of the structure of the pad portion 2 after remelting and hardening treatment according to this method (magnification: 400x) shows a complete chilled structure,
It can be seen that there is no precipitation of graphite or coarsening of the chill structure.

It should be noted that the present invention is not limited to the configuration of the above-mentioned embodiments, and may be modified and embodied as desired without departing from the spirit of the invention, for example, as described below.

(1> The cooling means 6 can also be pressed from the back side (lower side in FIG. 1) of the pad part 2 and the rib part 3. In other words, the cooling means 6 can be pressed against the part to be treated at a specific position. but not limited to.

(2) The present invention can also be embodied as a method and apparatus for remelting and hardening various cast iron castings other than rocker arms.

[Effects of the Invention] The method and apparatus for remelting and hardening cast iron castings of the present invention are configured as described above, so that even the treated part having a small volume and low self-cooling effect can be completely chilled. This has the excellent effect of preventing the precipitation of graphite and coarsening of the chilled structure and obtaining high hardness.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a remelting hardening treatment method and its apparatus according to an embodiment of the present invention, FIG. 2 is a side view,
FIG. 3 is a photograph of the structure after remelting and hardening treatment by the same method. FIG. 4 is a side view showing the conventional remelting hardening treatment method;
FIG. 5 is a cross-sectional view, and FIG. 6 is a photograph of the structure after remelting and hardening according to the conventional method. DESCRIPTION OF SYMBOLS 1... Rocker arm as a cast iron casting, 2... Pad part as a treated part, 4... Re-melting hardening treatment device, 5... Melting means, 6...
...Cooling means, 7...Pushing means.

Claims (2)

[Claims] 1. In a remelting hardening treatment method in which a treated part (2) of a cast iron casting (1) is heated and remelted, and the treated part (2) is chilled by self-cooling, the volume is small and the self-cooling effect is low. The cooling means (6) is pressed against the part to be treated (2) before, during or immediately after the heating, and the part to be treated (2) is cooled.
) A method for remelting and hardening cast iron castings, characterized by forced cooling. 2. A melting means (5) that heats and remelts the treated part (2) of the cast iron casting (1), a cooling means (6) that can be in close contact with the treated part (2), and the cooling means (6). Processed part (2)
A remelting and hardening treatment apparatus for cast iron castings, comprising a pressing means (7) for removably pressing the iron casting.