JPH0653893B2 - Exhaust valve manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an exhaust valve of an engine.

[Conventional technology]

For example, in an exhaust valve of a diesel engine, since the umbrella portion 2 is exposed to a heat load in a more severe chemical atmosphere than the shaft portion 3, it is generally made of austenitic heat-resistant steel as shown in the side view of FIG. It is made by butt-welding the formed umbrella portion 2 and the shaft portion 3 made of martensitic heat-resistant steel at the welded portion 4, and the heat treatment is performed according to the characteristics of the martensitic heat-resistant steel of the shaft portion as a whole. In general, it is quenched at about 1050 ℃ and tempered to 700-800 ℃.

This is because when the entire valve is heat-treated in accordance with the metallurgical characteristics of the austenitic heat-resistant steel of the umbrella part, its strength and toughness are reduced due to the change in the metal structure of the shaft part.

[Problems to be Solved by the Invention]

However, since the umbrella of this kind of exhaust valve is austenitic heat-resistant steel, its solution heat treatment is 1100 ~
It is desirable to perform the treatment at about 1200 ° C. in order to fully exhibit its corrosion resistance. In this respect, the conventional quenching temperature has not yet fully exerted the corrosion resistance of an expensive material.

Therefore, it is conceivable to induction-harden the umbrella portion, but there is a problem in that heating takes a considerable amount of time and thermal deformation occurs.

The present invention has been proposed in view of such circumstances, a long-life exhaust valve that rapidly heats only the surface layer without causing thermal deformation to sufficiently exhibit the heat resistance and corrosion resistance of austenitic heat-resistant steel. It aims at providing the manufacturing method of.

[Means for Solving the Problems]

Therefore, the present invention is an exhaust valve that heat-treats the whole in accordance with the metallurgical characteristics of the shaft portion after butt welding the head portion made of austenitic heat-resistant steel and the shaft portion made of martensitic heat-resistant steel. In the manufacturing method, after the heat treatment, when the valve is rotated around its central axis at an appropriate rotational speed, it is moved in the axial direction, while the direction of the laser beam is relatively changed while the bulb is rotated on the outer surface. It is characterized in that the outer surface is entirely quenched by being applied in the normal direction.

[Work]

With this structure, only the upper surface of the shaft that receives the sulfuric acid attack on the shaft side of the umbrella is heated rapidly by the laser beam without heat deformation, and only the surface layer is rapidly heated to improve the heat resistance and corrosion resistance of the austenitic heat resistant steel. It is possible to obtain a method of manufacturing a long-life exhaust valve that fully exhibits its properties.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view thereof.

In the above figure, the same reference numerals as in FIG. 2 indicate the same members as in the same figure, respectively, 5 is a laser light source, and 6 is a laser beam.

In such an arrangement, the exhaust valve 1 and the laser light source 5 are initially in the relational positions shown by solid lines, and the spot of the laser beam 6 is applied to the low-gradient portion a of the umbrella portion 2 of the exhaust valve 1 in the normal direction. Exhaust valve 1
Is fed axially downwardly to a position shown by a broken line at a constant speed while rotating at a constant speed around its central axis by means not shown, while the laser light source 5 is shown from a solid line position to a broken line position. It is rotated by means.

Then, first, the low-gradient portion a of the umbrella portion 2 and the steep-gradient portion b of the umbrella portion 2 are sequentially irradiated with the laser beam 6, and at that time, only the surface layer of the portion hit by the laser spot is instantly heated. As a result of being immediately cooled by air, it is quenched, and when the umbrella portion and the laser light source reach the position of the broken line, the upper surface of the umbrella portion is completely quenched.

During the above quenching, quenching is performed only on the surface layer of the small part irradiated by the laser spot, so no thermal deformation occurs on the whole, and the upper surface of the umbrella part is efficiently corroded and the austenitic heat resistant steel Improves to match metallurgical properties.

〔The invention's effect〕

In short, according to the present invention, an exhaust valve that heat-treats the entire body in accordance with the metallurgical characteristics of the shaft after butt-welding the umbrella part made of austenitic heat-resistant steel and the shaft made of martensitic heat-resistant steel. In the manufacturing method, after the heat treatment, when the valve is rotated around its central axis at an appropriate rotational speed, it is moved in the axial direction, while the direction of the laser beam is relatively changed while the valve is rotated to the outside. By quenching the outer surface as a whole by applying it to the surface in the normal direction, only the surface layer is rapidly heated without thermal deformation, and the heat resistance and corrosion resistance of austenitic heat-resistant steel can be fully exhibited. The present invention is extremely useful industrially because it provides a method of manufacturing a long-life exhaust valve.

[Brief description of drawings]

FIG. 1 is a layout drawing showing the hardening procedure of one embodiment of the present invention,
FIG. 2 is a side view showing an exhaust valve of a known diesel engine. 1 ... Exhaust valve, 2 ... Umbrella part, 3 ... Shaft part, 4 ... Welded part, 5 ... Laser light source, 6 ... Laser beam, a ... Low slope part, b ... Steep slope part

Claims (1)

[Claims] 1. An exhaust valve which is produced by butt-welding a head portion made of austenitic heat-resistant steel and a shaft portion made of martensitic heat-resistant steel, and then heat-treating the whole according to the metallurgical characteristics of the shaft portion. In the method, after the heat treatment, when the valve is rotated around its central axis at an appropriate rotational speed, it is moved in the axial direction, while the direction of the laser beam is relatively changed while the valve is applied to the outer surface. A method for manufacturing an exhaust valve, characterized in that the outer surface is entirely quenched by being applied in a normal direction.